code: private static Map<Direction, Map<Parity, String>> createBorders() {
          Map<Direction, Map<Parity, String>> m = createDirectionParityMap();
  
          m.get(Direction.RIGHT).put(Parity.EVEN, "bcfguvyz");
          m.get(Direction.LEFT).put(Parity.EVEN, "0145hjnp");
          m.get(Direction.TOP).put(Parity.EVEN, "prxz");
          m.get(Direction.BOTTOM).put(Parity.EVEN, "028b");
  
          addOddParityEntries(m);
          return m;
      }
docs: Returns a map to be used in hash border calculations.
  
  @return map of borders