Add napoleon for documentation

docs/source/conf.py

@@ -25,6 +25,7 @@ sys.path.insert(0, os.path.abspath('../..'))
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
 extensions = ['sphinx.ext.autodoc',
+              'sphinx.ext.napoleon',
               'sphinx.ext.pngmath',
               'sphinxcontrib.tikz',
               'sphinx_numfig']