code: def _mix(self, source, noise, snr):
      get_power = lambda x: np.mean(x**2)
      if get_power(noise):
          scl = np.sqrt(
              get_power(source)
              / (np.power(10, snr / 10) * get_power(noise))
          )
      else:
          scl = 0
      return 1 * source + scl * noise
  
imports: from pathlib import Path
  import numpy
  from math import ceil
  from fairseq.data.audio import rand_uniform
  from fairseq.data.audio.waveform_transforms import AudioWaveformTransform, register_audio_waveform_transform
label_desc: Use image node_id 5 for calling the NoiseAugmentTransform obj's underlying member method code with example usage: obj._mix(source, noise, snr) and returns: unknown