code: def print_token(self, token_node_index):
          
          err_msg = "The given node is not a token node."
          assert isinstance(self.nodes[token_node_index], TokenNode), err_msg
          onset = self.nodes[token_node_index].onset
          offset = self.nodes[token_node_index].offset
          return self.text[onset:offset]
docs: returns the string representation of a token.