Add collections.__all__ (#7296)

stdlib/collections/__init__.pyi

@@ -12,6 +12,8 @@ if sys.version_info >= (3, 10):
 else:
     from _collections_abc import *
 
+__all__ = ["ChainMap", "Counter", "OrderedDict", "UserDict", "UserList", "UserString", "defaultdict", "deque", "namedtuple"]
+
 _S = TypeVar("_S")
 _T = TypeVar("_T")
 _T1 = TypeVar("_T1")