code: def _load_audio_file(self):
          
          self._step_begin(u"load audio file")
          # NOTE file_format=None forces conversion to
          #      PCM16 mono WAVE with default sample rate
          audio_file = AudioFile(
              file_path=self.task.audio_file_path_absolute,
              file_format=None,
              rconf=self.rconf,
              logger=self.logger
          )
          audio_file.read_samples_from_file()
          self._step_end()
          return audio_file
docs: Load audio in memory.
  
          :rtype: :class:`~aeneas.audiofile.AudioFile`