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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 make_calls(self, num_calls=1):
 """Adds appropriate sleep to avoid making too many calls. Args: num_calls: int the number of calls which will be made """

        self._cull()
        while self._outstanding_calls + num_calls > self._max_calls_per_second:
            time.sleep(0)  # yield
            self._cull()

        self._call_times.append(self.CallRecord(time=time.time(), num_calls=num_calls))
        self._outstanding_calls += num_calls