code: def register_instances(self, instances):
          
          if isinstance(instances, str) or isinstance(instances, unicode):
              instances = [instances]
          new_instances = self.connection.register_instances(self.name, instances)
          self.instances = new_instances
docs: Adds instances to this load balancer. All instances must be in the same
          region as the load balancer. Adding endpoints that are already
          registered with the load balancer has no effect.
  
          :param list instances: List of instance IDs (strings) that you'd like
              to add to this load balancer.