'Remove Instances from an existing Load Balancer.
:type load_balancer_name: string
:param load_balancer_name: The name of the Load Balancer
:type instances: List of strings
:param instances: The instance ID\'s of the EC2 instances to remove.
:rtype: List of strings
:return: An updated list of instances for this Load Balancer.'

def deregister_instances(self, load_balancer_name, instances):

    params = {'LoadBalancerName': load_balancer_name}
    self.build_list_params(params, instances, 'Instances.member.%d.InstanceId')
    return self.get_list('DeregisterInstancesFromLoadBalancer', params, [('member', InstanceInfo)])
