def sky_bbox_ll(self):
        """
        The sky coordinates of the lower-left vertex of the minimal
        bounding box of the source segment, returned as a
        `~astropy.coordinates.SkyCoord` object.

        The bounding box encloses all of the source segment pixels in
        their entirety, thus the vertices are at the pixel *corners*.
        """

        if self._wcs is not None:
            return pixel_to_skycoord(self.xmin.value - 0.5,
                                     self.ymin.value - 0.5,
                                     self._wcs, origin=0)
        else:
            return None
The sky coordinates of the lower-left vertex of the minimal
        bounding box of the source segment, returned as a
        `~astropy.coordinates.SkyCoord` object.

        The bounding box encloses all of the source segment pixels in
        their entirety, thus the vertices are at the pixel *corners*.