inga.Graph.__init__ we can specifykey_to_id. I can't see any reason why thismust be astdlib.dict and not any other class that implements thetyping.Mapping protocol (__getitem__,__len__,__iter__). I have a usecase where I have a more memory efficient mapping than a dict and would like to use it.

However, whenever theid_to_key property is used, this will create a full inverse mapping, undoing any memory efficiency. It would be great to be able to pass an inverse mapping optionally (id_to_key) to avoid this calculation if possible. Currently I'm doing:

G=ga.Graph(...,key_to_id=...)G._id_to_key= ...

but obviously this relies on setting the 'private'_id_to_key member, which has no API stability guarantees. I'd be happy to implement this change!