code: def _find_usage_spot_instances(self):
          
          logger.debug('Getting spot instance request usage')
          try:
              res = self.conn.describe_spot_instance_requests()
          except botocore.exceptions.ClientError as e:
              if e.response['Error']['Code'] == 'UnsupportedOperation':
                  return
              raise
          count = 0
          for req in res['SpotInstanceRequests']:
              if req['State'] in ['open', 'active']:
                  count += 1
                  logger.debug('Counting spot instance request %s state=%s',
                               req['SpotInstanceRequestId'], req['State'])
              else:
                  logger.debug('NOT counting spot instance request %s state=%s',
                               req['SpotInstanceRequestId'], req['State'])
          self.limits['Max spot instance requests per region']._add_current_usage(
              count,
              aws_type='AWS::EC2::SpotInstanceRequest'
          )
docs: calculate spot instance request usage and update Limits