def flux(phys, eph, lam):
    """Model flux density for a given wavelength `lam`, or a list/array thereof

        Parameters
        ----------
        phys : `sbpy.data.Phys` instance, mandatory
            provide physical properties
        eph : `sbpy.data.Ephem` instance, mandatory
            provide object ephemerides
        lam : `astropy.units` quantity or list-like, mandatory
            wavelength or list thereof

        Examples
        --------
        >>> from astropy.time import Time
        >>> from astropy import units as u
        >>> from sbpy.thermal import STM
        >>> from sbpy.data import Ephem, Phys
        >>> epoch = Time('2019-03-12 12:30:00', scale='utc')
        >>> eph = Ephem.from_horizons('2015 HW', location='568', epochs=epoch) # doctest: +REMOTE_DATA
        >>> phys = PhysProp('diam'=0.3*u.km, 'pv'=0.3) # doctest: +SKIP
        >>> lam = np.arange(1, 20, 5)*u.micron # doctest: +SKIP
        >>> flux = STM.flux(phys, eph, lam) # doctest: +SKIP

        not yet implemented

        """
