def METHOD_NAME(self):
    """
        @outputs:
            appsecret_proof: HMAC-SHA256 hash of page access token
                using app_secret as the key
    """
    app_secret = str(self.app_secret).encode('utf8')
    access_token = str(self.access_token).encode('utf8')
    return hmac.new(app_secret, access_token, hashlib.sha256).hexdigest()