old_contents: # from time_frequency import Spectrogram, Melspectrogram
  # from utils import AmplitudeToDB, Normalization2D
  
  
new_contents: # from time_frequency import Spectrogram, Melspectrogram
  # from utils import AmplitudeToDB, Normalization2D
  
  from . import time_frequency
  from . import backend
  from . import backend_keras
  from . import stft
  from . import augmentation
  from . import filterbank
  from . import utils
  
  
subject: add some more on init