'#19298 -- MultiValueField needs to override the default as it needs
to deep-copy subfields:'

def test_multivalue_deep_copy(self):

    class ChoicesField(MultiValueField, ):
        def __init__(self, fields=(), *args, **kwargs):
            fields = (ChoiceField(label='Rank', choices=((1, 1), (2, 2))), CharField(label='Name', max_length=10))
            super().__init__(fields=fields, *args, **kwargs)
    field = ChoicesField()
    field2 = copy.deepcopy(field)
    self.assertIsInstance(field2, ChoicesField)
    self.assertIsNot(field2.fields, field.fields)
    self.assertIsNot(field2.fields[0].choices, field.fields[0].choices)
