Docstrings of __call__ are not rendered in HTML documentation

See for example the Bands documentation.

In the docstring of __call__ we actually specify how to call an instance of Bands, and specify some extra restrictions on the API (e.g. that the return order is ascending in energy).

I would be surprised if we were the first people to encounter the problem of needing to document callable objects properly. This will probably involve configuring sphinx in some esoteric way, or putting the __call__ docstring in the class docstring in such a way that sphinx displays it nicely.