typing.NamedTuple is used in two ways.

1. It is a callable which produces a new namedtuple type.
2. It can also be used as a base in the class statement for creating a new namedtuple type.

In both cases it is not a real class. You cannot create an instance of NamedTuple or a subclass of NamedTuple. But it is implemented as a class, and help() shows methods and data descriptors for it, which are useless.

The proposed PR implements NamedTuple like a function. Implementation of the __mro_entries__ method allows to use it as a base in the class statement.