for S1, S2 being vertex-disjoint GraphUnionSet
for G1 being GraphUnion of S1
for G2 being GraphUnion of S2 st S1,S2 are_isomorphic holds
ex S3 being vertex-disjoint GraphUnionSet ex E being Subset of (the_Edges_of G2) ex G3 being GraphUnion of S3 st
( S1,S3 are_Disomorphic & G3 is reverseEdgeDirections of G2,E )