// array is replaced on map because it is impossible
  // to calculate number of internal edges in advance
  // due to "internal edges"
  TColStd_DataMapOfIntegerInteger Internal;
...
    Internal.Bind(in, n[j]);
    Internal.Bind(in+1, n[k]);
    in += 2;
...
  TColStd_DataMapIteratorOfDataMapOfIntegerInteger aIt(Internal);
  for (; aIt.More(); aIt.Next()) {
    Standard_Integer n1 = aIt.Value();
    aIt.Next();
    Standard_Integer n2 = aIt.Value();
    dis.Draw(Nodes(n1).Transformed(tr),
         Nodes(n2).Transformed(tr));