def _is_valid_for ( self, object, name, value ):
        if self.is_valid_for( value ):
            return value

        self.error( object, name, value )
convert an hrn and type to a urn string
dataset/ETHPy150Open enthought/traits/traits/trait_handlers.py/TraitType._is_valid_for--crossover with--dataset/ETHPy150Open fp7-ofelia/ocf/expedient/src/python/sfa/util/namespace.py/hrn_to_urn