Currently we don't have full coverage for the line graphs generators. Code blocks which are highlighted with red at codcov https://app.codecov.io/gh/networkx/networkx/blob/main/networkx/generators/line.py don't have corresponding tests. The tests should be added in https://github.com/networkx/networkx/blob/main/networkx/generators/tests/test_line.py

Current Behavior

We don't test all the paths the code can take us.

Expected Behavior

We should be testing everything so there aren't any surprises.

Steps to Reproduce

Visit https://app.codecov.io/gh/networkx/networkx/blob/main/networkx/generators/line.py