docs: public static BidiFormatter getInstance(Dir contextDir) {
      switch (contextDir) {
        case LTR:
          return DEFAULT_LTR_INSTANCE;
        case RTL:
          return DEFAULT_RTL_INSTANCE;
        case NEUTRAL:
          throw new IllegalArgumentException("invalid context directionality: " + contextDir);
      }
      throw new AssertionError(contextDir);
    }