docs: def apply_noise(self, noise_generator, split_idx, ndigits=6):
          """Apply noise to dimensions within a peak.
  
          :param noise_generator: Noise generator object.
          :param int split_idx: Index specifying which peak list split parameters to use.
          :return: None
          :rtype: :py:obj:`None`
          """
          noise = noise_generator.generate(self.labels, split_idx)
          for dim, noise_value in zip(self, noise):
              dim.chemshift = round(dim.chemshift + noise_value, ndigits)