code: def effective_FPS(self):
          
          if self.start_time is None:
              self.start_time = 0
          elapsed = monotonic() - self.start_time
          return self.called / elapsed
docs: Calculates the effective frames-per-second - this should largely
          correlate to the desired FPS supplied in the constructor, but no
          guarantees are given.
  
          :returns: The effective frame rate.
          :rtype: float