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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 pad(self, pad_length):
 """ Pad the pianoroll with zeros at the end along the time axis. Parameters pad_length : int The length to pad with zeros along the time axis. """

        self.pianoroll = np.pad(
            self.pianoroll, ((0, pad_length), (0, 0)), 'constant')