static String name(int number)
    {
        switch (number)
        {
            case ID_ENUM_VALUE:
                return STR_ENUM_VALUE;
            case ID_ENUM:
                return STR_ENUM;
            default:
                return null;
        }
    }
Used when a field is declared as {@code Enum<?>} (with or with-out generics).

@author David Yu
@created Apr 25, 2012
protostuff-runtime/src/main/java/io/protostuff/runtime/PolymorphicEnumSchema.java