code: private int[] neighbors(ITetrahedralChirality element, Map<IAtom, Integer> map) {
          IAtom[] atoms = element.getLigands();
          int[] vs = new int[atoms.length];
          for (int i = 0; i < atoms.length; i++)
              vs[i] = map.get(atoms[i]);
          return vs;
      }
docs: Access the neighbors of {@code element} as their indices.
  
  @param element tetrahedral element
  @param map     atom index lookup
  @return the neighbors