docs: def getchannel(samples: np.ndarray, ch:int) -> np.ndarray:
      """
      Returns a view into a channel of samples.
  
      samples    : a numpy array representing the audio data
      ch         : the channel to extract (channels begin with 0)
      """
      N = numchannels(samples)
      if ch > (N - 1):
          raise ValueError("channel %d out of range" % ch)
      if N == 1:
          return samples
      return samples[:, ch]