Fix `add_sequence_neighbour_vector`

anton-bushuiev commented 1 year ago

Hi, @a-r-j 👋! Currently, add_sequence_neighbour_vector has two bugs:

If conditions for adjacency fail, the vec from the previous iteration (pair of adjacent residues) is being used. So, the errors propagate silently. I fixed it to put zeros when conditions fail.
It does not handle insertion codes. Currently, I fixed it by parsing node ids first, but there probably may be a better way to get insertions.

I have also removed a redundant check for chain identity when iterating through the nodes of the same chain, and added a test.

[x] Added a note about the modification or contribution to the ./CHANGELOG.md file (if applicable)
[x] Added appropriate unit test functions in the ./graphein/tests/* directories (if applicable)
[x] Modify documentation in the corresponding Jupyter Notebook under ./notebooks/ (if applicable)
[x] Ran python -m py.test tests/ and make sure that all unit tests pass (for small modifications, it might be sufficient to only run the specific test file, e.g., python -m py.test tests/protein/test_graphs.py)
[ ] Checked for style issues by running black . and isort .