def pyramid(self, n_levels=3, downscale=2):
        r"""
        Return a rescaled pyramid of this image. The first image of the
        pyramid will be the original, unmodified, image, and counts as level 1.

        Parameters
        ----------
        n_levels : `int`, optional
            Total number of levels in the pyramid, including the original
            unmodified image
        downscale : `float`, optional
            Downscale factor.

        Yields
        ------
        image_pyramid: `generator`
            Generator yielding pyramid layers as :map:`Image` objects.
        """
        image = self
        yield image
        for _ in range(1 - n_levels):
            image = image.rescale(1.0 / downscale)
            yield image
dataset/ETHPy150Open menpo/menpo/menpo/image/base.py/Image.pyramid/swapped operands of `-`