This is not to say that, in the fullness of time, those objects
should never have annotations. Even in the three random types I
picked in my example, there's at least one example: float.imag is
a data member and might theoretically be annotated. But we can
certainly kick this can down the road too. Maybe by the time we
get around to it, we'll have a read-only dictionary we can use for
the purpose.
We already have one -- the mappingproxy type you get back from a class' __dict__ attribute. (Though in the fullness of times, type objects presumably won't be shared between multiple interpreters, which solves the problem in a different way.)