def METHOD_NAME(self, client):
    input_ap_obj = PetAPObject(
        id = 2,
        name = 'Hira',
        additional_properties = {
            'siblings': [{
                'id': 1,
                'name': 'Puppy',
                'birthdate': '2017-12-13T02:29:51Z',
                'complexProperty': {
                    'color': 'Red'
                }
            }],
            'picture': '//////4='
        }
    )
    output_ap_obj = client.pets.create_ap_object(input_ap_obj)
    assert output_ap_obj.additional_properties['siblings'][0]['birthdate'] ==  '2017-12-13T02:29:51Z'