code: static private Map<String, TEnum> extractEnumMap(Class<? extends TEnum> enumClass) {
      ImmutableMap.Builder<String, TEnum> builder = ImmutableMap.builder();
      for(TEnum e : enumClass.getEnumConstants()) {
        builder.put(e.toString(), e);
      }
      return builder.build();
    }
docs: returns 'enum name -> enum object' mapping.
  Currently used for converting Tuple to a Thrift object.