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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def post_session():
 """ This endpoint appears to be required in order to keep pubnub updates flowing for some user. This just posts a random nonce to the /users/me/session endpoint and returns the result. """


    url_string = "{}/users/me/session".format(WinkApiInterface.BASE_URL)

    nonce = ''.join([str(random.randint(0, 9)) for i in range(9)])
    _json = {"nonce": str(nonce)}

    try:
        arequest = requests.post(url_string,
                                 data=json.dumps(_json),
                                 headers=API_HEADERS)
        response_json = arequest.json()
        return response_json
    except requests.exceptions.RequestException:
        return None