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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 getThroughput(self, instId: int) -> float: """ Return the throughput of the specified instance. :param instId: the id of the protocol instance """

        # We are using the instanceStarted time in the denominator instead of
        # a time interval. This is alright for now as all the instances on a
        # node are started at almost the same time.
        if instId not in self.instances.ids:
            return None
        perf_time = time.perf_counter()
        throughput = self.throughputs[instId].get_throughput(perf_time)
        return throughput