code: def clip(self, lower=0, upper=127):
          
          for track in self.tracks:
              track.clip(lower, upper)
docs: Clip the pianorolls of all tracks by the given lower and upper bounds.
  
          Parameters
          ----------
          lower : int or float
              The lower bound to clip the pianorolls. Defaults to 0.
          upper : int or float
              The upper bound to clip the pianorolls. Defaults to 127.