Missing block function return statements

[palomena]

Many "block" (as in widget) functions do not return anything even though they should.

For example in d3blocks.py, line 1963 is missing a return keyword. If it is not specified, the html is not returned in case filepath is None. Simply changing it to

return self.D3graph.show(figsize=figsize, title=title, filepath=filepath, showfig=showfig, overwrite=overwrite, show_slider=show_slider, set_slider=set_slider)

fixes it.
This is not the only function that has this quirk, many others do not return a value too. But some others like tree() do return a value. This seems like inconsistent API design or a bug.