Python Mock で オリジナルのインスタンメソッドのを呼びたい時

import os
import requests

from urllib3.poolmanager import PoolManager
from requests.adapters import HTTPAdapter
from urllib3.poolmanager import PoolManager, proxy_from_url
from mock import patch
import urllib3


ORIGINAL_METHOD = urllib3.connection.HTTPConnection.putrequest

def patched_method(self, *args, **kwargs):
    return ORIGINAL_METHOD(self, *args, **kwargs)

class ProxyHeaderHttpAdapter(HTTPAdapter):
    def proxy_headers(self, proxy):
        headers = super(ProxyHeaderHttpAdapter, self).proxy_headers(proxy)
        headers = {
            'User-Agent': 'tunneling',
            'Connection': 'Keep-Alive',
            'Pragma': 'no-cache',
        }
        headers.update(headers)
        return headers


def main():
    session = requests.Session()

    adapters = ProxyHeaderHttpAdapter(max_retries=3)
    session.mount("http://", adapters)
    session.mount("https://", adapters)

    proxy =  {"http":"127.0.0.1:8888", "https":"127.0.0.1:8888"}
    if proxy != {}:
        session.proxies = proxy
        session.verify = None

    url = 'https://www.google.com'
    with patch.object(urllib3.connection.HTTPConnection, 'putrequest', side_effect=patched_method, autospec=True):
        session.get(url)


if __name__ == "__main__":
    os.chdir(os.path.dirname(os.path.abspath(__file__)))
    main()

autospec と sideeffect を組み合わせるのが解決策だった。