def METHOD_NAME():
    c = C(10)
    assert c.prop_x == 10
    c.prop_x = 20
    assert c.prop_x == 20
    del c.prop_x
    not_found = False
    try:
        c.prop_x
    except AttributeError:
        not_found = True
    assert not_found
    d = D(10)
    assert d.prop_x == 10
    d.prop_x = 20
    assert d.prop_x == 20
    del d.prop_x
    not_found = False
    try:
        d.prop_x
    except AttributeError:
        not_found = True
    assert not_found
    assert X.prop_x is not Y.prop_x