def channel_axis(self, batch):
axis = self.__model.channel_axis()<EOL>if not batch:<EOL><INDENT>axis = axis - <NUM_LIT:1><EOL><DEDENT>return axis<EOL>
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.