[docs] [issue39426] Pickler docstring misstates default and highest protocols

Change by miss-islington <mariatta.wijaya+miss-islington@gmail.com>: ---------- pull_requests: +17549 pull_request: https://github.com/python/cpython/pull/18162 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue39426> _______________________________________