.Container = Trait { .__contains__ = (self: Self) -> Bool }
.Hashable = Trait { .__hash__ = (self: Self) -> Nat }
.Sized = Trait { .__len__ = (self: Self) -> Nat }
# TODO: varargs
.Callable = Trait { .__call__ = (self: Self) -> Obj }
# .Iterator T = Trait { .__next__ = (self: Self) -> T }
.Iterator = Trait { .__next__ = (self: Self) -> Obj }
# .Iterable T = Trait { .__iter__ = (self: Self) -> Iterator T }
.Iterable = Trait { .__iter__ = (self: Self) -> .Iterator }
.Collection = Subsume .Container and .Iterable
.Reversible = Trait { .__reversed__ = (self: Self) -> .Iterator }
.Genertor = Subsume .Iterator
.Sequence = Subsume .Collection and .Sized and .Reversible