mitmproxy: full replace responce via script

What is best practice for replace response via mitmproxy My steps:

1. write script (see below)
2. run mitmdump -p 8080 -s myplugin.py
3. open browser and via mitmproxy go to http://ift.tt/2nwb63x I got a blank screen (load a bit a page)
4. open http://ift.tt/2nwb63x via curl with mitmproxy and get other bit of page

What is the best practice for replace response from one server to other server. plugin code:

def response(flow):
    new_resp = requests.get('https://google.com')

    new_resp_headers=dict(new_resp.headers.items())

    #prepare byte headers
    byte_headers = [(str.encode(k), str.encode(v)) for k, v in new_resp_headers.items()]

    #replace responce
    flow.response.status_code = new_resp.status_code
    flow.response.content = new_resp.content
    flow.response.data.headers = Headers(byte_headers)

another way is is

new_resp = Response.make(200,authenticated_responce.content,byte_headers )
flow.response = new_resp

call AttributeError: 'Response' object has no attribute 'is_replay'

What is true method for this? Site for replace is may be reach with ajax html5 and other technology