Initial roots should be at depth 0 instead of -1

[bjchambers]

Describe the bug
Currently, the results of start_k are added at depth 0, while initial_root_ids the neighbors of initial_root_ids are treated as depth 0 (making the initial roots effectively depth -1). This leads to confusing explanations of how the traversals behave.

To Reproduce
Read the docs at https://datastax.github.io/graph-rag/get-started/traversal/

Expected behavior
Initial roots should be roots (depth 0) and returned.

Ideally, the docs for traverse and atraverse should also clarify that initial_root_ids and start_k are combined, therefore start_k=0 should be used if you only want initial roots. Possibly a warning too?

[bjchambers]

@kerinin filed this for the depth of the initial roots. Thoughts on anywhere else it could/should be documented?

[epinzur]

I think this should be an option. I can see where both cases could be desirable.

When initial roots are desired to be part of the output, then they should be added at depth=0. When they are not, it should continue to work as it does now (depth==-1).

[epinzur]

I would change this to a feature-request instead of a bug.