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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 snapshot(self):
 """ Snapshot the application state. Snapshots are used to restore the application state, either after a restart or a crash. """

        with self._lock:
            current_state = self.state_manager.current_state
            state_change_id = self.state_change_id

            # otherwise no state change was dispatched
            if state_change_id:
                self.storage.write_state_snapshot(state_change_id, current_state)