docstring for _conj_action
rename label -> actions_dict for clarity
take conjunctions of multiple env,sys actions guarding transitions

and unit test
override __init__, __str__, update, setdefault in TypedDict

because they do not call __setitem__ in the standard library implementation of dict
mv TypedDict from labeled_graphs to mathset
tests for TypedDict
check for untyped attribute keys in LabeledDiGraph.add_node, .add_edge
rewrite LabeledDiGraph test