Only expose the abstract base classes.

The concrete types are for internal use (registration).
Keep from accidentally resurrecting the types module in collections.

Lib/_abcoll.py

@@ -18,11 +18,6 @@ __all__ = ["Hashable", "Iterable", "Iterator",
            "MappingView", "KeysView", "ItemsView", "ValuesView",
            "Sequence", "MutableSequence",
            "ByteString",
-           "bytearray_iterator", "bytes_iterator", "dict_itemiterator",
-           "dict_items", "dict_keyiterator", "dict_keys", "dict_proxy",
-           "dict_valueiterator", "dict_values", "list_iterator",
-           "list_reverseiterator", "range_iterator", "set_iterator",
-           "str_iterator", "tuple_iterator", "zip_iterator",
            ]