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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 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)