code: def _custom_token_stream(self):
      
      token_stream = default_make_token_stream(self)
      for processor in _token_stream_processors:
          token_stream = processor(token_stream)
      return token_stream
docs: A wrapper for the BaseEnamlLexer's make_token_stream which allows
      the stream to be customized by adding "token_stream_processors".
      
      A token_stream_processor is a generator function which takes the 
      token_stream as it's single input argument and yields each processed token 
      as it's output. Each token will be an instance of `ply.lex.LexToken`.