docs: function getDirection(
    str: string,
    strongFallback: ?BidiDirection,
  ): BidiDirection {
    if (!strongFallback) {
      strongFallback = UnicodeBidiDirection.getGlobalDir();
    }
    invariant(
      UnicodeBidiDirection.isStrong(strongFallback),
      'Fallback direction must be a strong direction',
    );
    return resolveBlockDir(str, strongFallback);
  }