for S being vertex-disjoint GraphUnionSet
for G being GraphUnion of S holds
( ( S is non-multi implies G is non-multi ) & ( G is non-multi implies S is non-multi ) & ( S is non-Dmulti implies G is non-Dmulti ) & ( G is non-Dmulti implies S is non-Dmulti ) & ( S is acyclic implies G is acyclic ) & ( G is acyclic implies S is acyclic ) )