class Foo(HasProps): x = DataSpec("xfield", default=12)
class Foo(HasProps): x = DataSpec("xfield")
class Foo(HasProps): y = DataSpec(default=12)
class Foo(HasProps): y = DataSpec("yfield", default=12)
class Foo(HasProps): x = DataSpec("xfield", default=12)
class Foo(HasProps): x = DataSpec("xfield")
class Foo(HasProps): y = DataSpec(default=12)
class Foo(HasProps): y = DataSpec("yfield", default=12)