Adding bidirectional dijkstra to graphs

[armingh2000]

There are 3 implementations of Dijkstra in graphs dir, but none is bidirectional.
I can implement the algorithm if it's needed.
+: Is it worth to change each directory's files, so that all inputs of classes and functions are in a specific format which is accepted by all other related functions and methods?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[cclauss]

Please feel free to submit pull requests without waiting for permission. It is easier for maintainers review Python code then English prose. ;-) Normalizing the function call parameters only makes sense if you are going to create performance benchmarks so we can have an bake-off.