code: def _rfind(expr, sub, start=0, end=None):
      
  
      return _string_op(expr, RFind, output_type=types.int64,
                        _sub=sub, _start=start, _end=end)
docs: Return highest indexes in each strings in the sequence or scalar
      where the substring is fully contained between [start:end]. Return -1 on failure.
      Equivalent to standard str.rfind().
  
      :param expr:
      :param sub:
      :param start:
      :param end:
      :return: sequence or scalar