DOC: Fix coremath.rst to fix refguide_check (#15718)

* DOC: fix coremath.rst to fix refguide_check

Co-authored-by: Eric Wieser <wieser.eric@gmail.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/doc/source/reference/c-api/coremath.rst b/doc/source/reference/c-api/coremath.rst
index 4200f4ba8..0c46475cf 100644
--- a/doc/source/reference/c-api/coremath.rst
+++ b/doc/source/reference/c-api/coremath.rst
@@ -249,9 +249,14 @@ Linking against the core math library in an extension
 To use the core math library in your own extension, you need to add the npymath
 compile and link options to your extension in your setup.py:
 
+        .. hidden in a comment so as to be included in refguide but not rendered documentation
+                >>> import numpy.distutils.misc_util
+                >>> config = np.distutils.misc_util.Configuration(None, '', '.')
+                >>> with open('foo.c', 'w') as f: pass
+
         >>> from numpy.distutils.misc_util import get_info
         >>> info = get_info('npymath')
-        >>> config.add_extension('foo', sources=['foo.c'], extra_info=info)
+        >>> _ = config.add_extension('foo', sources=['foo.c'], extra_info=info)
 
 In other words, the usage of info is exactly the same as when using blas_info
 and co.