Python has a unique approach to static typing. Python programs can contain type annotations, and even access those annotations at run time, but the annotations aren't evaluated by default. Instead, it is up to external programs to ascribe meaning to those annotations. The annotations themselves can be arbitrary Python expressions, but in practice usually involve using helpers from the built-in typing module, the meanings of which external type-checkers mostly agree upon. Yet the type system implicitly defined by the typing module and common type-checkers is insufficiently powerful to model all of the kinds of dynamic metaprogramming found in real-world Python programs. PEP 827 ("Type Manipulation") aims to add additional capabilities to Python's type system to fix this, but discussion of the PEP has been of mixed sentiment.