The typing module: Support for gradual typing as defined by PEP 484.
At large scale, the structure of the module is following:
-* Imports and exports, all public names should be explicitelly added to __all__.
+* Imports and exports, all public names should be explicitly added to __all__.
* Internal helper functions: these should never be used in code outside this module.
* _SpecialForm and its instances (special forms): Any, NoReturn, ClassVar, Union, Optional
* Two classes whose instances can be type arguments in addition to types: ForwardRef and TypeVar