Sizeof is not relevant to the built-in functions as far as I know. It is already described at <https://docs.python.org/dev/library/sys.html#sys.getsizeof>.

Some more delegations that I think should be documented here (at least for Python 3):

* abs() -> object.__abs__()
* bytes() -> object.__bytes__()
* complex() -> object.__complex__()
* divmod() -> object.__divmod__()
* float() -> object.__float__(). The text is already there, but there is no hyperlink.
* hex() -> object.__index__(). Also just needs a hyperlink.
* isinstance() -> class.__instancecheck__()
* issubclass() -> class.__subclasscheck__()
* pow() -> object.__pow__()
* round() -> object.__round__()

I added some comments about the sorted() specification on Reitveld, but maybe they should be handled in a separate issue, because the delegation is less direct compared to the other functions being considered here. And any update to sorted() should probably also consider list.sort(), min(), max(), and maybe the bisect and heapq modules.