len (the_arity_of (@ set-constr )) = card ((set-constr `2 ) `1 ) by ABCMIZ_1:def 24
.= card ([{} ,0 ] `1 ) by MCART_1:7
.= card 0 by MCART_1:7 ;
hence the_arity_of (@ set-constr ) = {} ; :: according to ABCMIZ_A:def 13 :: thesis: verum