set G2 = G .set (OrderingSelector,X);
A1:
(G .set (OrderingSelector,X)) . WeightSelector = G . WeightSelector
by GLIB_003:def 1, GLIB_000:9;
WeightSelector in dom G
by GLIB_003:def 4;
then
WeightSelector in (dom G) \/ {OrderingSelector}
by XBOOLE_0:def 3;
then A2:
WeightSelector in dom (G .set (OrderingSelector,X))
by GLIB_000:7;
the_Edges_of G = the_Edges_of (G .set (OrderingSelector,X))
by Lm1, GLIB_000:10;
then
(G .set (OrderingSelector,X)) . WeightSelector is ManySortedSet of the_Edges_of (G .set (OrderingSelector,X))
by A1, GLIB_003:def 4;
hence
G .set (OrderingSelector,X) is [Weighted]
by A2, GLIB_003:def 4; verum