Deprecate creating a :class:`typing.NamedTuple` class using keyword
arguments to denote the fields (NT = NamedTuple("NT", x=int, y=str)).
Use the class-based syntax or the functional syntax instead.
Two methods of creating NamedTuples with 0 fields using the functional
syntax are also deprecated: NT = NamedTuple("NT") and NT =
NamedTuple("NT", None). To create a NamedTuple class with 0 fields,
either use class NT(NamedTuple): ... or NT = NamedTuple("NT", []).