How to restrict asssignment to TypeVar to Hashable?

I want to restrict TypeVar role to Hashable.
For example,

def convert_to_set(x: List[T]) -> Set[T]:
    return set(x)

I want to indicate that T is subclass of Hashable, because all elements of set must be hashable.

One of the solution I thought is the following:

TH = TypeVar("TH", Hashable, Hashable)

However, I think this is ugly.

What should I do?