chore: use if TYPE_CHECKING: blocks (#2866)

unit_test/oci_container_test.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import contextlib
 import json
 import os
@@ -7,7 +9,6 @@ import subprocess
 import sys
 import textwrap
 import time
-from collections.abc import Iterator
 from contextlib import nullcontext
 from pathlib import Path, PurePath, PurePosixPath
 
@@ -25,6 +26,10 @@ from cibuildwheel.oci_container import (
     _check_engine_version,
 )
 
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from collections.abc import Iterator
+
 # Test utilities
 
 # for these tests we use manylinux2014 images, because they're available on