Helper for matplotlib imshow

def extent(self):
        """Helper for matplotlib imshow"""
        return (
            self.intervals[1].pix1 - 0.5,
            self.intervals[1].pix2 - 0.5,
            self.intervals[0].pix1 - 0.5,
            self.intervals[0].pix2 - 0.5,
        )