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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 close(self, end_time=None):
 """ Close the trace entity by setting `end_time` and flip the in progress flag to False. Also decrement parent segment's ref counter by 1. :param int end_time: Epoch in seconds. If not specified current time will be used. """

        super(Subsegment, self).close(end_time)
        self.parent_segment.decrement_ref_counter()