Simplify code with ruff --fix

[cclauss]

ruff --select=B009,RET503,ANN204,SIM108,SIM201 --fix .

• https://beta.ruff.rs/docs/rules

[RonnyPfannschmidt]

Adding none return annotations to untyped code seems like noise

[cclauss]

I find return None to be a helpful reminder of the possibilities and it does not really slow me down when reading code. Explicit is better than implicit.

I can revert if that is the consensus.

Or perhaps at line 34, we should:

if not cov_datafile:
    return None

and then dedent the next ~25 lines of code.

[RonnyPfannschmidt]

The return that was added is great

The type annotations for only the return type none are noise, I'd strongly prefer to have those be added as part of full annotation at a later point