[BugFix, Feature] Fix KeyError in NXGraphCompiler and extending the class of embeddable graphs to unit disk graphs

[lmoroml]

This pull request introduces the following improvements and bug fixes:

1. Fix for KeyError in NXGraphCompiler: an issue was identified where a KeyError: "x" occurred when a NetworkX graph was passed to the NXGraphCompiler. This error was caused by a missing check for the existence of the "x" attribute in the graph. The fix involves adding a validation step to ensure that the "x" attribute is present before it is accessed.

2. New Method: is_unit_disk_graph: a new method, is_unit_disk_graph(), has been added to the BaseGraph class. This method provides a straightforward way to check whether a graph is a unit disk graph, rather than a disk graph.

3. Update to is_embeddable Method: the is_embeddable() method has been modified to use is_unit_disk_graph() rather than the previous is_disk_graph() method. The change was made because the old implementation, which used a radius of min_atom_distance + epsilon, while correct in theory, unnecessarily limited the class of embeddable graphs. By restricting embeddability to only those unit disk graphs with edges between min_atom_edge_distance and min_atom_edge_distance + epsilon, the method was excluding graphs that should have been considered embeddable. The new approach broadens the criteria allowing to embed unit disk graphs.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 2.77778% with 35 lines in your changes missing coverage. Please review.

Project coverage is 38.81%. Comparing base (ddc8cee) to head (2f10e4d).

Files with missing lines	Patch %	Lines
tests/test_graphs.py	0.00%	20 Missing ⚠️
qek/data/graphs.py	6.25%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #116      +/-   ##
==========================================
- Coverage   39.91%   38.81%   -1.11%     
==========================================
  Files          17       17              
  Lines        1175     1211      +36     
  Branches      136      140       +4     
==========================================
+ Hits          469      470       +1     
- Misses        677      712      +35     
  Partials       29       29              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Yoric]

Thanks for the PR, I'll try and review it by tomorrow.

[RolandMacDoland]

Thanks a lot @lmoroml nice work indeed :) LGTM. Minor comments.

[Yoric]

My apologies for the delay, I've been sick :/

Looks good to me, thanks for the PR!