Helper method to find the deployment label that the stage_name is currently associated with.

def _get_current_deployment_label(self):
        '''
        Helper method to find the deployment label that the stage_name is currently associated with.
        '''
        deploymentId = self._get_current_deployment_id()
        deployment = __salt__['boto_apigateway.describe_api_deployment'](restApiId=self.restApiId,
                                                                         deploymentId=deploymentId,
                                                                         **self._common_aws_args).get('deployment')
        if deployment:
            return deployment.get('description')
        return None