The typing module documentation page has a very long section "Classes, functions, and decorators" (https://docs.python.org/3/library/typing.html#classes-functions-and-decorators) that should be split in subsections. The ordering of the entries seems haphazard: it's not alphabetical. Its grouped according to invisible categories. 

The categories appear as comments in the source code of typing.py: the `__all__` global lists the API split into categories (see below). We should add these categories to the page as subsections of "Classes, functions, and decorators"

- Super-special typing primitives.
- ABCs (from collections.abc).
- Structural checks, a.k.a. protocols.
- Concrete collection types.