Bases: astropy.coordinates.RepresentationMapping
This namedtuple is used with the frame_specific_representation_info attribute to tell frames what attribute names (and default units) to use for a particular representation. reprname and framename should be strings, while defaultunit can be either an astropy unit, the string 'recommended' (to use whatever the representation’s recommended_units is), or None (to indicate that no unit mapping should be done).