def test_default_pool_key_funcs_copy(self) -> None:
        """Assert each PoolManager gets a copy of ``pool_keys_by_scheme``."""
        p = PoolManager()
        assert p.key_fn_by_scheme == p.key_fn_by_scheme
        assert p.key_fn_by_scheme is not key_fn_by_scheme
Assert each PoolManager gets a copy of ``pool_keys_by_scheme``.
test/test_poolmanager.py