Squashed commit of the following:

commit 7307b2d
Author: Hepheir <[email protected]>
Date:   Wed Jun 2 01:19:42 2021 +0900

    Remove all except `DOMString`

commit e9134ff
Author: Hepheir <[email protected]>
Date:   Mon May 31 20:48:17 2021 +0900

    Change the type of `DOMString` from `TypeVar` into `str`

Related issues:
- Implement of `DOMString` type #18

Author: hepheir

w3/python/core/type.py

@@ -1,8 +1 @@
-from __future__ import absolute_import
-
-from typing import TypeVar
-
-
 DOMString = str
-
-AnyNode = TypeVar('AnyNode')