Delete cached copies of this broadcast on the executors. If the
        broadcast is used after this is called, it will need to be
        re-sent to each executor.

        :param blocking: Whether to block until unpersisting has completed

def unpersist(self, blocking=False):
        """
        Delete cached copies of this broadcast on the executors. If the
        broadcast is used after this is called, it will need to be
        re-sent to each executor.

        :param blocking: Whether to block until unpersisting has completed
        """
        if self._jbroadcast is None:
            raise Exception("Broadcast can only be unpersisted in driver")
        self._jbroadcast.unpersist(blocking)