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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 validate_session(self, token, remote="127.0.0.1", proxy=None):
 """Validate a session token. Validate a previously acquired session token against the Crowd server. This may be a token provided by a user from a http cookie or by some other means. Args: token: The session token. remote: The remote address of the user. proxy: Value of X-Forwarded-For server header Returns: dict: A dict mapping of user attributes if the application authentication was successful. See the Crowd documentation for the authoritative list of attributes. None: If authentication failed. """


        params = {
            "validationFactors": [
                {"name": "remote_address", "value": remote, },
            ]
        }

        if proxy:
            params["validation-factors"]["validationFactors"].append({"name": "X-Forwarded-For", "value": proxy, })

        url = self.rest_url + "/session/%s" % token
        response = self._post(url, data=json.dumps(params), params={"expand": "user"})

        # For consistency between methods use None rather than False
        # If token validation failed for any reason return None
        if not response.ok:
            return None

        # Otherwise return the user object
        return response.json()