[docker] Fix Container.attach() return type (#15155)

stubs/docker/@tests/test_cases/check_attach.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from typing_extensions import assert_type
+
+from docker.models.containers import Container
+
+
+def check_attach(c: Container) -> None:
+    assert_type(c.attach(), bytes)
+    assert_type(c.attach(stream=False), bytes)
+    for line in c.attach(stream=True):
+        assert_type(line, bytes)