def output(self):
        """
        Returns the next available output token.

        :return: the next token, None if none available
        :rtype: Token
        """
        if (self._output is None) or (len(self._output) == 0):
            result = None
        else:
            result = self._output.pop(0)
        return result
Returns the next available output token.

        :return: the next token, None if none available
        :rtype: Token