docs: 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)