for S1, S2 being Graph-membered set st S1 c= S2 holds
( the_Vertices_of S1 c= the_Vertices_of S2 & the_Edges_of S1 c= the_Edges_of S2 & the_Source_of S1 c= the_Source_of S2 & the_Target_of S1 c= the_Target_of S2 )