Point out that the setdefault defaults the value to None.  Inspired by Michael Chermside's thinking about patch #748126 (the chief upshot of which thinking was "reject it!").
Point out that the setdefault defaults the value to None.  Inspired by
Michael Chermside's thinking about patch #748126 (the chief upshot of
which thinking was "reject it!").

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator