Missing optional dependencies / documentation for used packages

[KS-HTK]

Issue

When using simple_plotly with the on_map parameter there is a function call to validate that the geodata is in fact on the map, it uses geopy to do this. geopy is not in the dependencies/optional dependencies for pandapower.

For this case the docs also make no mention that geopy might be used/required by simple_plotly.

I think all used dependencies should at least be listed once in any of the optional dependency categories, and should appear under the all keyword if they are called by pandapower code. Implicite requirements might break if the dependency that requires that package might remove it from there dependencies at any time.

How is this currently handled? Is there a preferred method, as this is not the only package I found that is not listed anywhere?