docs: def classes_file(flag_leaf=False):
      """All known File* classes
  
      Args:
          flag_leaf: returns only classes that do not have subclasses
                     ("leaf" nodes as in a class tree graph)
      """
      if __flag_first:
          __setup()
  
      if not flag_leaf:
          return _classes_file
  
      return [cls for cls in _classes_file if cls not in _classes_file_superclass]