
theorem
  for G1 being _Graph, G2, G3 being removeParallelEdges of G1
  holds G3 is G2-isomorphic
proof
  let G1 be _Graph, G2, G3 be removeParallelEdges of G1;
  G1 is G1-isomorphic by Th53;
  hence thesis by Th168;
end;
