Return a 4-cornered polygon equivalent to this rectangle

def to_polygon(self):
        """
        Return a 4-cornered polygon equivalent to this rectangle
        """
        x,y = self.corners.T
        vertices = PixCoord(x=x, y=y)
        return PolygonPixelRegion(vertices=vertices, meta=self.meta,
                                  visual=self.visual)