calculate spot fleet request usage and update Limits

def _find_usage_spot_fleets(self):
        """calculate spot fleet request usage and update Limits"""
        logger.debug('Getting spot fleet request usage')
        try:
            res = self.conn.describe_spot_fleet_requests()
        except botocore.exceptions.ClientError as e:
            if e.response['Error']['Code'] == 'UnsupportedOperation':
                return
            raise
        if 'NextToken' in res:
            logger.error('Error: describe_spot_fleet_requests() response '
                         'includes pagination token, but pagination not '
                         'configured in awslimitchecker.')
        active_fleets = 0
        total_target_cap = 0
        lim_cap_per_fleet = self.limits['Max target capacity per spot fleet']
        lim_launch_specs = self.limits[
            'Max launch specifications per spot fleet']
        for fleet in res['SpotFleetRequestConfigs']:
            _id = fleet['SpotFleetRequestId']
            if fleet['SpotFleetRequestState'] != 'active':
                logger.debug('Skipping spot fleet request %s in state %s',
                             _id, fleet['SpotFleetRequestState'])
                continue
            active_fleets += 1
            cap = fleet['SpotFleetRequestConfig']['TargetCapacity']
            launch_specs = len(
                fleet['SpotFleetRequestConfig']['LaunchSpecifications'])
            total_target_cap += cap
            lim_cap_per_fleet._add_current_usage(
                cap, resource_id=_id, aws_type='AWS::EC2::SpotFleetRequest')
            lim_launch_specs._add_current_usage(
                launch_specs, resource_id=_id,
                aws_type='AWS::EC2::SpotFleetRequest')
        self.limits['Max active spot fleets per region']._add_current_usage(
            active_fleets, aws_type='AWS::EC2::SpotFleetRequest'
        )
        self.limits['Max target capacity for all spot '
                    'fleets in region']._add_current_usage(
            total_target_cap, aws_type='AWS::EC2::SpotFleetRequest'
        )