def METHOD_NAME():
    with pytest.raises(stix2.exceptions.InvalidValueError) as excinfo:
        stix2.v21.Grouping(id='my-prefix--', **GROUPING_KWARGS)
    assert excinfo.value.cls == stix2.v21.Grouping
    assert excinfo.value.prop_name == "id"
    assert excinfo.value.reason == "must start with 'grouping--'."
    assert str(excinfo.value) == "Invalid value for Grouping 'id': must start with 'grouping--'."