Regex for part of a files contents to include

[uncenter]

I don't see a way to specify a regex for what parts of a file to include. It also doesn't help that look-around, including look-ahead and look-behind, is not supported. I'd like to be able to do something like this:

[type.python]
extend-include-re = [
  # Only spellcheck comments
  "#.*"
]