code: def __call__(self, x, uttid=None, train=True):
      if not train:
          return x
  
      x = x.astype(numpy.float32)
  
      if self.accept_uttid:
          ratio = self.utt2ratio[uttid]
      else:
          ratio = self.state.uniform(self.lower, self.upper)
      if self.dbunit:
          ratio = 10 ** (ratio / 20)
      return x * ratio
  
imports: import librosa
  import numpy
  import scipy
  import soundfile
  from espnet.utils.io_utils import SoundHDF5File
label_desc: Use image node_id 3 for calling the VolumePerturbation obj's underlying member method code with example usage: obj.__call__(x, uttid, train) and returns: unknown, x