class Foo(object): x = my_attr.ib(default=sentinel)
class Point2(object): z = my_attr.ib() y = my_attr.ib() x = my_attr.ib()
class Point1(object): x = my_attr.ib() y = my_attr.ib() z = my_attr.ib()
class Foo(object): bar = my_attr.ib(default=None)
class Foo(object): bar = my_attr.ib(None)
class foo(object): bar = my_attr.ib(3)