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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def note2snd(pitch, quarters):
 """ Creates an audio Stream object for a single note. Parameters pitch : Pitch note like ``"A4"``, as a string, or ``None`` for a rest. quarters : Duration in quarters (see ``quarter_dur``). """

  dur = quarters * quarter_dur
  if pitch is None:
    return zeros(dur)
  freq = str2freq(pitch) * Hz
  return synth(freq, dur)