Clean up method `skip_if_sam`

* Reword the docstring with nicer prose.
* Change variable names for the sake of clarity.
* Use a list comprehension instead of a map-and-lambda combo.

A list comprehension is used instead of a map-and-lambda combo because:

* List comprehensions are more common, and in my opinion more readable. When in
  Rome...
* There is anecdotal evidence that list comprehensions are preferred by the
  community at large. See the comments to PEP 279.
* Pylint complains about the usage of a map-and-lambda combo when a list
  comprehension suffices.
* Last and least, list comprehensions are more efficent.