code: def _dcp_flatten(fs):
      """Flatten spectrograms for DeepChromaProcessor. Needs to be outside
      of the class in order to be picklable for multiprocessing.
      """
      return np.concatenate(fs).reshape(len(fs), -1)
  
imports: from __future__ import absolute_import, division, print_function
  import warnings
  import numpy
  from madmom.audio.filters import A4, Filterbank, PitchClassProfileFilterbank, HarmonicPitchClassProfileFilterbank
  from madmom.audio.spectrogram import Spectrogram, FilteredSpectrogram, SemitoneBandpassSpectrogram
  from madmom.processors import SequentialProcessor, Processor
label_desc: Use image node_id 1 for calling a global function with example usage: _dcp_flatten(fs) and returns: np