code: def normalized_weighted_phase_deviation(spectrogram, epsilon=EPSILON):
      """
      Normalized Weighted Phase Deviation.
  
      Parameters
      ----------
      spectrogram : :class:`Spectrogram` instance
          :class:`Spectrogram` instance.
      epsilon : float, optional
          Add `epsilon` to the `spectrogram` avoid division by 0.
  
      Returns
      -------
      normalized_weighted_phase_deviation : numpy array
          Normalized weighted phase deviation onset detection function.
  
      References
      ----------
      .. [1] Simon Dixon,
             "Onset Detection Revisited",
             Proceedings of the 9th International Conference on Digital Audio
             Effects (DAFx), 2006.
  
      """
      if epsilon <= 0:
          raise ValueError(
              "a positive value must be added before division"
          )
      # normalize WPD by the sum of the spectrogram
      # (add a small epsilon so that we don't divide by 0)
      norm = np.add(np.mean(spectrogram, axis=1), epsilon)
      return np.asarray(weighted_phase_deviation(spectrogram) / norm)
  
imports: from __future__ import absolute_import, division, print_function
  import numpy
  from scipy.ndimage import maximum_filter, minimum_filter, uniform_filter
  from ..audio.signal import smooth
  from ..processors import BufferProcessor, OnlineProcessor, ParallelProcessor, SequentialProcessor
  from ..utils import combine_events
label_desc: Use image node_id 12 for calling a global function with example usage: normalized_weighted_phase_deviation(spectrogram, epsilon) and returns: np