* toying around with a graph using networkx layouting
* basic implementation and documentation of a class for undirected graphs
* import graph module into global namespace
* add graph module to documentation
* poetry: add networkx as a dependency
* remove some debug prints
* sort all extracted mobjects w.r.t. z_index
* add test for z_index (from #327)
* more complex z_index test
* black
* improve imports
* use z_index to have edges below vertices
* add type hints
* rename some tests to make space for graph tests
* fix problem with manual positioning
* add test
* black
* new animate syntax
* document label_fill_color
