code: @Override
      public String indexValue(String name, Object value) {
          if (value == null) {
              return null;
          } else if (value instanceof Boolean) {
              return (Boolean) value ? TRUE : FALSE;
          } else if (value instanceof String) {
              String s = (String) value;
              if (s.equalsIgnoreCase(TRUE)) {
                  return TRUE;
              } else if (s.equalsIgnoreCase(FALSE)) {
                  return FALSE;
              }
          }
          throw new IllegalArgumentException();
      }
docs: {@inheritDoc}