def wait(self, index, next_index=None):
        """
        Block until it is the turn indicated by index.
        :param index:
        :param next_index: Set the index to this value after finishing. Releases the process waiting on next_index.
            Defaults to incrementing index by 1.
        :return:
        """
        return OrderedBarrier.Guard(self, index, index+1 if next_index is None else next_index)
Block until it is the turn indicated by index.
        :param index:
        :param next_index: Set the index to this value after finishing. Releases the process waiting on next_index.
            Defaults to incrementing index by 1.
        :return: