PR Summary

All's in the title. (The two functions have the same implementation.)

Note that the following lines in sankey.py seem just wrong:

        if labels != '' and getattr(labels, '__iter__', False):
            # np.iterable() isn't used because it would give True if labels is
            # a string

(str does have an __iter__).

PR Checklist

• Has Pytest style unit tests
• Code is Flake 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way