code: def pad_to_multiple(self, factor):
          
          remainder = self.pianoroll.shape[0] % factor
          if remainder:
              pad_width = ((0, (factor - remainder)), (0, 0))
              self.pianoroll = np.pad(self.pianoroll, pad_width, 'constant')
docs: Pad the pianoroll with zeros at the end along the time axis with the
          minimum length that makes the resulting pianoroll length a multiple of
          `factor`.
  
          Parameters
          ----------
          factor : int
              The value which the length of the resulting pianoroll will be
              a multiple of.