new_contents: 
  def handle(instance):
      from core.models import Controller, ControllerSlice, ControllerNetwork, NetworkSlice
  
      networks = [ns.network for ns in NetworkSlice.objects.filter(slice=instance.slice)]
      controller_networks = ControllerNetwork.objects.filter(network__in=networks,
                                                                  controller=instance.node.site_deployment.controller)
  
      for cn in controller_networks:
          if (cn.lazy_blocked):	
  		cn.lazy_blocked=False
  		cn.backend_register = '{}'
  		cn.save()
  
subject: replace Sliver with Instance