Document how to declare dependant types in method signatures

I have several TypedDict:

TerminateHandlerContextType = TypedDict( "TerminateHandlerContextType",{...},)
CrashHandlerContextType = TypedDict( "CrashHandlerContextType", {... },)
QuitHandlerContextType = TypedDict("QuitHandlerContextType", {...})

And then related Callable:

TerminateHandlerType = Callable[[TerminateHandlerContextType], None]
QuitHandlerType = Callable[[QuitHandlerContextType], None]
CrashHandlerType = Callable[[CrashHandlerContextType], None]

If I then declare a method that depends of both:

    def _call_handler(
    self,
    handler: Union[
        TerminateHandlerType, QuitHandlerType, CrashHandlerType
    ],
    context: Union[
         TerminateHandlerContextType, QuitHandlerContextType, CrashHandlerContextType,
    ],
    ):
        ...
        return handler(context) # <---- MYPY COMPLAINS HERE

Then mypy complains, because, while I always ensure logically that the proper handler is called with the proper context, it can't see that.

I couldn't find in the documentation a way to tell it that the context type depends on the handler type. I assume it's either a Generic, or a TypeVar, but didn't find the solution.

mypy 0.770
python 3.6

No documentation file, test, or entry point is named in the issue. First determine which mypy documentation section covers dependent relationships between handler and context types, then verify the documented approach against the TypedDict and Callable example. Done means the documentation explains how to express or handle this relationship and addresses the reported type-checking complaint.