The ArrowStyle docstrings should be converted into numpydoc-compatible strings. The current ones can be seen from here downwards: http://matplotlib.org/devdocs/api/patches_api.html?highlight=arrowstyle#matplotlib.patches.ArrowStyle.BarAB

See https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt for a guide to converting to a compatible docstring.