code: @Nullable
    protected String getParentPath(String path) {
      // Root does not have a parent.
      if (isRoot(path)) {
        return null;
      }
      int separatorIndex = path.lastIndexOf(PATH_SEPARATOR);
      if (separatorIndex < 0) {
        return null;
      }
      return path.substring(0, separatorIndex);
    }
docs: Get parent path.
  
  @param path ufs path including scheme and bucket
  @return the parent path, or null if the parent does not exist