code: def empty(self, duration):
          '''Empty chord annotations
  
          Parameters
          ----------
          duration : number
              The length (in seconds) of the empty annotation
  
          Returns
          -------
          ann : jams.Annotation
              A chord annotation consisting of a single `no-chord` observation.
          '''
          ann = super(ChordTransformer, self).empty(duration)
  
          ann.append(time=0,
                     duration=duration,
                     value='N', confidence=0)
  
          return anf empty(self, duration):
          '''Empty chord annotations
  
          Parameters
          ----------
          duration : number
              The length (in seconds) of the empty annotation
  
          Returns
          -------
          ann : jams.Annotation
              A chord annotation consisting of a single `no-chord` observation.
          '''
          ann = super(ChordTransformer, self).empty(duration)
  
          ann.append(time=0,
                     duration=duration,
                     value='N', confidence=0)
  
          return ann
docs: Empty chord annotations
  
          Parameters
          ----------
          duration : number
              The length (in seconds) of the empty annotation
  
          Returns
          -------
          ann : jams.Annotation
              A chord annotation consisting of a single `no-chord` observation.