# File lib/fog/aws/models/elb/load_balancer.rb, line 31
        def register_instances(instances)
          requires :id
          data = connection.register_instances_with_load_balancer(instances, id).body['RegisterInstancesWithLoadBalancerResult']
          data['Instances'].map!{|h| h['InstanceId']}
          merge_attributes(data)
        end