def _query_string(self):
        if not self.valid:
            raise UnvalidatedRequest("This request is invalid or has not"
                "been validated.")
        parameters = {
            "response_type":self.response_type,
            "client_id":self.client_id}
        if self.redirect_uri is not None:
            parameters["redirect_uri"] = self.redirect_uri
        if self.state is not None:
            parameters["state"] = self.state
        if self.scope is not None:
            parameters["scope"] = ' '.join(self.scope)
        return urlencode(parameters)
Scenario: Successfully creating local association object:
dataset/ETHPy150Open hiidef/oauth2app/oauth2app/authorize.py/Authorizer._query_string--crossover with--dataset/ETHPy150Open bigmlcom/python/bigml/tests/test_28_association.py/TestAssociation.test_scenario3