code: def __refill_tokenbuffer(self):
          
          if len(self.tokens) == 0:
              self.__tokenize(self.dxfile.readline())
docs: Add a new tokenized line from the file to the token buffer.
  
          __refill_tokenbuffer()
  
          Only reads a new line if the buffer is empty. It is safe to
          call it repeatedly.
  
          At end of file, method returns empty strings and it is up to
          __peek and __consume to flag the end of the stream.