docs: def check(src, dst):  # type: (str,str)->None
      """
      Code take from black formatter. Just want to see if this is still python.
      :param src:
      :return:
      """
      was_bad = False
      try:
          _ = ast.parse(src)
      except Exception as exc:
          was_bad = True
          major, minor = sys.version_info[:2]
          logger.warning(
              "failed to parse source file "
              "with Python {0}.{1}'s builtin AST. Switch to manual "
              "or stop using deprecated Python 2 syntax. AST error message: {2}".format(
                  major, minor, exc
              )
          )
  
      try:
          _ = ast.parse(dst)
      except Exception as exc:
          if was_bad:
              # I didn't make it worse.
              pass
          else:
              # ok, this made the file worse. It must be jiggle_version's fault.
              print(dst)
              logger.error(dst)
              raise