PEP8 correction; "block comment should start with '# '"
Indented comment to match block
PEP8 corrections; remove redundant parens and indentation correction
PEP8; block comment should start with "# "
PEP8; block comment should start with "# "
`if not in` statement correction
Code clarity: Remove redundant TYPE_CHOICES dict comprehension, Python 2.7 doesn't have dictionary comprehension.