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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 __unbind_call(self, still_valid):
 """ Calls the iPOPO unbind method """

        with self._lock:
            if self.__timer is not None:
                # Timeout expired, we're not valid anymore
                self.__timer = None
                self.__still_valid = still_valid
                self._ipopo_instance.unbind(
                    self, self.__timer_args[0], self.__timer_args[1]
                )