code: public SquarePlanar normalize() {
          int cfg = getConfigOrder();
          if (cfg == 1)
              return this;
          IAtom[] carriers = invapply(getCarriers().toArray(new IAtom[4]),
                                       PERMUTATIONS[cfg-1]);
          return new SquarePlanar(getFocus(),
                                  carriers,
                                  SPU);
      }
docs: Normalize the configuration to the lowest configuration order (1) -
  U-shaped.
  @return the normalized configuration