code: def channel_axis(self, batch):
          
          axis = self.__model.channel_axis()
          if not batch:
              axis = axis - 1
          return axis
docs: Interface to model.channel_axis for attacks.
  
          Parameters
          ----------
          batch : bool
              Controls whether the index of the axis for a batch of images
              (4 dimensions) or a single image (3 dimensions) should be returned.