def METHOD_NAME():
    client = boto3.client("forecast", region_name=region)
    client.create_dataset_group(DatasetGroupName="hello", Domain="CUSTOM")
    result = client.list_dataset_groups()
    assert len(result["DatasetGroups"]) == 1
    assert result["DatasetGroups"][0]["DatasetGroupArn"] == (
        f"arn:aws:forecast:{region}:{ACCOUNT_ID}:dataset-group/hello"
    )