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