def to_str(obj):
    if type(obj) in (list, tuple):
        string = "/".join([item.__name__ for item in obj])
    else:
        string = obj.__name__
    return string
order_by property splits field by comma and returns multiple.
dataset/ETHPy150Open Relrin/aiorest-ws/aiorest_ws/utils/validators.py/to_str--crossover with--dataset/ETHPy150Open mozilla/moztrap/tests/view/lists/test_sort.py/SortTest.test_order_by_multiple_asc