code: def fix_e731(self, result):
          
          (line_index, _, target) = get_index_offset_contents(result,
                                                              self.source)
          match = LAMBDA_REGEX.search(target)
          if match:
              end = match.end()
              self.source[line_index] = '{}def {}({}): return {}'.format(
                  target[:match.start(0)], match.group(1), match.group(2),
                  target[end:].lstrip())
docs: Fix do not assign a lambda expression check.