docs: def get_category_aliases_under(parent_alias=None):
      """Returns a list of category aliases under the given parent.
  
      Could be useful to pass to `ModelWithCategory.enable_category_lists_editor`
      in `additional_parents_aliases` parameter.
  
      :param str|None parent_alias: Parent alias or None to categories under root
      :rtype: list
      :return: a list of category aliases
      """
      return [ch.alias for ch in get_cache().get_children_for(parent_alias, only_with_aliases=True)]