[Feature] Get the type of generic typeVar in class

Feature

Having a class inheriting from a Generic make it possible to get type of the typeVar, possibly with a method like get_type or alike.

class MyClass(Generic[T]):
    def __init__(self):
         self.generic_type = T.get_type()

Pitch

Other languages' type system have this capability.

e.g.

C#;
Type type = abc.GetType().GetGenericArguments()[0];
https://stackoverflow.com/questions/557340/how-to-get-the-type-of-t-from-a-member-of-a-generic-class-or-method

C++;

template <class T>
class MyClass : public Base<T>
{
public:
    T t;
    decltype(t) t2;
};

https://en.cppreference.com/w/cpp/language/decltype

No files, tests, or entry points are identified in the issue, so begin by locating mypy's handling of Generic classes and type variables. Done would require an agreed design and implementation that lets a generic class obtain its type variable's type, with tests demonstrating the requested behavior.