code: def whitespace_around_operator(logical_line):
      r
      for match in OPERATOR_REGEX.finditer(logical_line):
          before, after = match.groups()
  
          if '\t' in before:
              yield match.start(1), "E223 tab before operator"
          elif len(before) > 1:
              yield match.start(1), "E221 multiple spaces before operator"
  
          if '\t' in after:
              yield match.start(2), "E224 tab after operator"
          elif len(after) > 1:
              yield match.start(2), "E222 multiple spaces after operator"
docs: r"""Avoid extraneous whitespace around an operator.
  
      Okay: a = 12 + 3
      E221: a = 4  + 5
      E222: a = 4 +  5
      E223: a = 4\t+ 5
      E224: a = 4 +\t5