Fix DisplayCommandBase comments for cliff Lister subclass tests

As bug #1477199 describes, the wrong comment below is all over the
unit test code of OSC.

    # DisplayCommandBase.take_action() returns two tuples

There is no such class named DisplayCommandBase in OSC. It is in cliff.

All OSC command classes inherit from the base classes in cliff,
class Command, class Lister and class ShowOne. It is like this:

Object
|--> Command
     |--> DisplayCommandBase
          |--> Lister
          |--> ShowOne

take_action() is an abstract method of class Command, and generally is
overwritten by subclasses.
* Command.take_action() returns nothing.
* Lister.take_action() returns a tuple which contains a tuple of columns
  and a generator used to generate the data.
* ShowOne.take_action() returns an iterator which contains a tuple of
  columns and a tuple of data.

So, this problem should be fixed in 3 steps:
1. Remove all DisplayCommandBase comments for tests of classes inheriting
   from class Command in cliff as it returns nothing.
2. Fix all DisplayCommandBase comments for tests of classes inheriting
   from class Lister in cliff. Lister.take_action() returns a tuple and
   a generator.
3. Fix all DisplayCommandBase comments for tests of classes inheriting
   from class ShowOne in cliff. ShowOne.take_action() returns two tuples.

This patch finishes step 2 in all but identity tests. There are too many
such comments in identity tests. So fix them all in another patch.

Change-Id: I00f38d12f55abe20fa708f6349073da658622f8d
Partial-bug: #1477199

11 files changed, 138 insertions, 46 deletions

diff --git a/openstackclient/tests/common/test_availability_zone.py b/openstackclient/tests/common/test_availability_zone.py
index e44455c7..feecaf55 100644
--- a/openstackclient/tests/common/test_availability_zone.py
+++ b/openstackclient/tests/common/test_availability_zone.py
@@ -144,7 +144,9 @@ class TestAvailabilityZoneList(TestAvailabilityZone):
         verifylist = []
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.compute_azs_mock.list.assert_called_with()
@@ -170,7 +172,9 @@ class TestAvailabilityZoneList(TestAvailabilityZone):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.compute_azs_mock.list.assert_called_with()
@@ -199,7 +203,9 @@ class TestAvailabilityZoneList(TestAvailabilityZone):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.compute_azs_mock.list.assert_called_with()
@@ -221,7 +227,9 @@ class TestAvailabilityZoneList(TestAvailabilityZone):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.compute_azs_mock.list.assert_not_called()
@@ -243,7 +251,9 @@ class TestAvailabilityZoneList(TestAvailabilityZone):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.compute_azs_mock.list.assert_not_called()
diff --git a/openstackclient/tests/common/test_extension.py b/openstackclient/tests/common/test_extension.py
index 21c2cc24..66532827 100644
--- a/openstackclient/tests/common/test_extension.py
+++ b/openstackclient/tests/common/test_extension.py
@@ -63,7 +63,9 @@ class TestExtensionList(TestExtension):
         verifylist = []
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # no args should output from all services
@@ -93,7 +95,9 @@ class TestExtensionList(TestExtension):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # no args should output from all services
@@ -131,7 +135,9 @@ class TestExtensionList(TestExtension):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.identity_extensions_mock.list.assert_called_with()
diff --git a/openstackclient/tests/common/test_module.py b/openstackclient/tests/common/test_module.py
index 6918c1b4..2821da9e 100644
--- a/openstackclient/tests/common/test_module.py
+++ b/openstackclient/tests/common/test_module.py
@@ -62,7 +62,9 @@ class TestCommandList(utils.TestCommand):
         verifylist = []
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         collist = ('Command Group', 'Commands')
@@ -94,7 +96,9 @@ class TestModuleList(utils.TestCommand):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Additional modules may be present, just check our additions
@@ -110,7 +114,9 @@ class TestModuleList(utils.TestCommand):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Additional modules may be present, just check our additions
diff --git a/openstackclient/tests/common/test_timing.py b/openstackclient/tests/common/test_timing.py
index e7b9a040..c4c738b2 100644
--- a/openstackclient/tests/common/test_timing.py
+++ b/openstackclient/tests/common/test_timing.py
@@ -61,7 +61,9 @@ class TestTiming(utils.TestCommand):
         verifylist = []
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.assertEqual(self.columns, columns)
@@ -80,7 +82,9 @@ class TestTiming(utils.TestCommand):
         verifylist = []
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.assertEqual(self.columns, columns)
         datalist = [
diff --git a/openstackclient/tests/image/v1/test_image.py b/openstackclient/tests/image/v1/test_image.py
index afe8c75a..7044ea1d 100644
--- a/openstackclient/tests/image/v1/test_image.py
+++ b/openstackclient/tests/image/v1/test_image.py
@@ -273,7 +273,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             detailed=True,
@@ -294,7 +296,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             detailed=True,
@@ -316,7 +320,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             detailed=True,
@@ -336,7 +342,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             detailed=True,
@@ -385,7 +393,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             detailed=True,
@@ -411,7 +421,9 @@ class TestImageList(TestImage):
         verifylist = [('sort', 'name:asc')]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             detailed=True,
diff --git a/openstackclient/tests/image/v2/test_image.py b/openstackclient/tests/image/v2/test_image.py
index 0da84a4e..3c478b53 100644
--- a/openstackclient/tests/image/v2/test_image.py
+++ b/openstackclient/tests/image/v2/test_image.py
@@ -495,7 +495,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with()
 
@@ -514,7 +516,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             public=True,
@@ -535,7 +539,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             private=True,
@@ -556,7 +562,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with(
             shared=True,
@@ -574,7 +582,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with()
 
@@ -620,7 +630,9 @@ class TestImageList(TestImage):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with()
         sf_mock.assert_called_with(
@@ -643,7 +655,9 @@ class TestImageList(TestImage):
         verifylist = [('sort', 'name:asc')]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
         self.api_mock.image_list.assert_called_with()
         si_mock.assert_called_with(
diff --git a/openstackclient/tests/network/v2/test_network.py b/openstackclient/tests/network/v2/test_network.py
index f96497a4..9829d578 100644
--- a/openstackclient/tests/network/v2/test_network.py
+++ b/openstackclient/tests/network/v2/test_network.py
@@ -380,7 +380,9 @@ class TestListNetwork(TestNetwork):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.network.networks.assert_called_with()
@@ -397,7 +399,9 @@ class TestListNetwork(TestNetwork):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.network.networks.assert_called_with(
@@ -416,7 +420,9 @@ class TestListNetwork(TestNetwork):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.network.networks.assert_called_with()
diff --git a/openstackclient/tests/network/v2/test_router.py b/openstackclient/tests/network/v2/test_router.py
index 98e9f17a..69c548a0 100644
--- a/openstackclient/tests/network/v2/test_router.py
+++ b/openstackclient/tests/network/v2/test_router.py
@@ -201,7 +201,9 @@ class TestListRouter(TestRouter):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.network.routers.assert_called_with()
@@ -217,7 +219,9 @@ class TestListRouter(TestRouter):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.network.routers.assert_called_with()
diff --git a/openstackclient/tests/object/v1/test_container.py b/openstackclient/tests/object/v1/test_container.py
index d34d73e2..62dc4f73 100644
--- a/openstackclient/tests/object/v1/test_container.py
+++ b/openstackclient/tests/object/v1/test_container.py
@@ -156,7 +156,9 @@ class TestContainerList(TestContainer):
         verifylist = []
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -188,7 +190,9 @@ class TestContainerList(TestContainer):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -222,7 +226,9 @@ class TestContainerList(TestContainer):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -255,7 +261,9 @@ class TestContainerList(TestContainer):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -287,7 +295,9 @@ class TestContainerList(TestContainer):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -328,7 +338,9 @@ class TestContainerList(TestContainer):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
diff --git a/openstackclient/tests/object/v1/test_object.py b/openstackclient/tests/object/v1/test_object.py
index f0d62f6e..431ab472 100644
--- a/openstackclient/tests/object/v1/test_object.py
+++ b/openstackclient/tests/object/v1/test_object.py
@@ -67,7 +67,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         o_mock.assert_called_with(
@@ -96,7 +98,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -126,7 +130,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -156,7 +162,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -186,7 +194,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -216,7 +226,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -247,7 +259,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
@@ -294,7 +308,9 @@ class TestObjectList(TestObject):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         # Set expected values
diff --git a/openstackclient/tests/object/v1/test_object_all.py b/openstackclient/tests/object/v1/test_object_all.py
index a90e5b65..f36d2ea7 100644
--- a/openstackclient/tests/object/v1/test_object_all.py
+++ b/openstackclient/tests/object/v1/test_object_all.py
@@ -102,7 +102,9 @@ class TestObjectList(TestObjectAll):
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
-        # DisplayCommandBase.take_action() returns two tuples
+        # In base command class Lister in cliff, abstract method take_action()
+        # returns a tuple containing the column names and an iterable
+        # containing the data to be listed.
         columns, data = self.cmd.take_action(parsed_args)
 
         self.assertEqual(self.columns, columns)