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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def print_token(self, token_node_index):
 """returns the string representation of a token."""

        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]