code: def empty(self, duration):
          '''Empty label annotations.
  
          Constructs a single observation with an empty value (None).
  
          Parameters
          ----------
          duration : number > 0
              The duration of the annotation
          '''
          ann = super(DynamicLabelTransformer, self).empty(duration)
          ann.append(time=0, duration=duration, value=None)
          return anf empty(self, duration):
          '''Empty label annotations.
  
          Constructs a single observation with an empty value (None).
  
          Parameters
          ----------
          duration : number > 0
              The duration of the annotation
          '''
          ann = super(DynamicLabelTransformer, self).empty(duration)
          ann.append(time=0, duration=duration, value=None)
          return ann
docs: Empty label annotations.
  
          Constructs a single observation with an empty value (None).
  
          Parameters
          ----------
          duration : number > 0
              The duration of the annotation