code: def _find_usage_spot_fleets(self):
          
          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'
          )
docs: calculate spot fleet request usage and update Limits