Earth really needs to be somewhere in the name of the function, too.  Otherwise, it would be natural to assume a sun position would be relative to the solarsystem barycenter.  Also, I'd call it Inertial instead of ICRF.  Technically it's J2000, but in Cesium we're using ICRF because it's close enough.  By calling it inertial we can gloss over that technicality.