def push_concurrency_history_item(self, state, number_concurrent_threads):
        """Adds a new concurrency-history-item to the history item list

        A concurrent history item stores information about the point in time where a certain number of states is
        launched concurrently
        (e.g. in a barrier concurrency state).

        :param state: the state that launches the state group
        :param number_concurrent_threads: the number of states that are launched
        """
        last_history_item = self.get_last_history_item()
        return_item = ConcurrencyItem(state, self.get_last_history_item(),
                                      number_concurrent_threads, state.run_id,
                                      self.execution_history_storage)
        return self._push_item(last_history_item, return_item)
Adds a new concurrency-history-item to the history item list

        A concurrent history item stores information about the point in time where a certain number of states is
        launched concurrently
        (e.g. in a barrier concurrency state).

        :param state: the state that launches the state group
        :param number_concurrent_threads: the number of states that are launched