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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 clip(self, lower=0, upper=127):
 """ 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. """

        for track in self.tracks:
            track.clip(lower, upper)