code: @Override
      public EUI64 unmarshal(String str) throws Exception {
          return str == null ? null : EUI64.fromString(str);
      }
docs: Converts the EUI-64 string representation in {@code str} to an {@link EUI64}. Returns
  {@code null} if {@code str} is {@code null}.
  
  @param str The EUI-64 string representation.
  @return The {@link EUI64} represented by {@code str}.
  @throws IllegalArgumentException if {@code str} is not a valid EUI-64 string representation.
  @see EUI64#fromString(String)