code: private void reflect(IntStack stack, IAtom beg, IAtom end) {
          Point2d begP = beg.getPoint2d();
          Point2d endP = end.getPoint2d();
          reflect(stack, begP, endP);
      }
docs: Reflect all atoms (indexes) int he provided stack around the line formed
  of the beg and end atoms.
  
  @param stack atom indexes to reflect
  @param beg   beg atom of a bond
  @param end   end atom of a bond