code: def _filtering_step(self, basename):
          
          name = ''.join(basename.split('.')[:-1])
          # May cause problems if wav is not less than 9 channels.
          if basename.split('.')[-1] == "wav":
              if self.get_verbosity():
                  print("Found wave! Copying to {}/filtered/{}".format(
                      self.src_dir, basename))
              subprocess.Popen(["cp", "{}/{}.wav".format(self.src_dir, name),
                                "{}/filtered/{}.wav".format(self.src_dir, name)],
                               universal_newlines=True).communicate()
docs: Moves the audio file if the format is `wav` to `filtered` directory.
  
          Parameters
          ----------
          basename : str
              A basename of `/home/random-guy/some-audio-file.wav` is
              `some-audio-file.wav`