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

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)]