def __init__(self, lens_galaxies, image_plane_grid_stack, border=None, cosmology=cosmo.Planck15,<EOL>units_distance='<STR_LIT>', units_luminosity='<STR_LIT>', units_mass='<STR_LIT>'):
if not lens_galaxies:<EOL><INDENT>raise exc.RayTracingException('<STR_LIT>')<EOL><DEDENT>image_plane = pl.Plane(galaxies=lens_galaxies, grid_stack=image_plane_grid_stack, border=border,<EOL>compute_deflections=True, cosmology=cosmology)<EOL>super(TracerImagePlane, self).__init__(planes=[image_plane], cosmology=cosmology)<EOL>
Ray tracer for a lens system with just an image-plane. 

        As there is only 1 plane, there are no ray-tracing calculations. This class is therefore only used for fitting \ 
        image-plane galaxies with light profiles.

        This tracer has only one grid-stack (see grid_stack.GridStack) which is used for ray-tracing.

        Parameters
        ----------
        lens_galaxies : [Galaxy]
            The list of lens galaxies in the image-plane.
        image_plane_grid_stack : grid_stacks.GridStack
            The image-plane grid stack which is traced. (includes the regular-grid, sub-grid, blurring-grid, etc.).
        border : masks.RegularGridBorder
            The border of the regular-grid, which is used to relocate demagnified traced pixels to the \
            source-plane borders.
        cosmology : astropy.cosmology
            The cosmology of the ray-tracing calculation.