code: def _ProcessAudio(self, tag, wall_time, step, audio):
      
      event = AudioEvent(wall_time=wall_time,
                         step=step,
                         encoded_audio_string=audio.encoded_audio_string,
                         content_type=audio.content_type,
                         sample_rate=audio.sample_rate,
                         length_frames=audio.length_frames)
      self.audios.AddItem(tag, event)
docs: Processes a audio by adding it to accumulated state.