Iterate over unique items in a python iterable

unique.py

from typing import Iterable, Hashable


def iterate_uniquely(items: Iterable[Hashable]):
    already_emitted = set()
    for item in items:
        key = hash(item)
        if key not in already_emitted:
            yield item
            already_emitted.add(key)


assert list(iterate_uniquely([1, 2, 3])) == [1, 2, 3]
assert list(iterate_uniquely([1, 3, 2, 3])) == [1, 3, 2]
assert list(iterate_uniquely([(1, 2), (1, 3), (2, 1)])) == [(1, 2), (1, 3), (2, 1)]
assert list(iterate_uniquely([(1, 2), (1, 3), (2, 1), (2, 1)])) == [(1, 2), (1, 3), (2, 1)]