old_contents: 
  def handle(controller):
      from core.models import Controller, Site, ControllerSite, Slice, ControllerSlice, User, ControllerUser
      from collections import defaultdict
  
      # relations for all sites
      ctrls_by_site = defaultdict(list)
      ctrl_sites = ControllerSite.objects.all()
      for ctrl_site in ctrl_sites:
          ctrls_by_site[ctrl_site.site].append(ctrl_site.controller)
      sites = Site.objects.all()
      for site in sites:
          if site not in ctrls_by_site or \
              controller not in ctrls_by_site[site]:
              controller_site = ControllerSite(controller=controller, site=site)
              controller_site.save()
      # relations for all slices
      ctrls_by_slice = defaultdict(list)
      ctrl_slices = ControllerSlice.objects.all()
      for ctrl_slice in ctrl_slices:
          ctrls_by_slice[ctrl_slice.slice].append(ctrl_slice.controller)
      slices = Slice.objects.all()
      for slice in slices:
          if slice not in ctrls_by_slice or \
              controller not in ctrls_by_slice:
              controller_slice = ControllerSlice(controller=controller, slice=slice)
              controller_slice.save()
      # relations for all users
      ctrls_by_user = defaultdict(list)
      ctrl_users = ControllerUser.objects.all()
      for ctrl_user in ctrl_users:
          ctrls_by_user[ctrl_user.user].append(ctrl_user.controller)
      users = User.objects.all()
      for user in users:
          if user not in ctrls_by_user or \
              controller not in ctrls_by_user[user]:
              controller_user = ControllerUser(controller=controller, user=user)
              controller_user.save()
  
new_contents: 
  def handle(controller):
      from core.models import Controller, Site, ControllerSite, Slice, ControllerSlice, User, ControllerUser, ControllerImages, ControllerNetwork
      from collections import defaultdict
  
      # relations for all sites
      ctrls_by_site = defaultdict(list)
      ctrl_sites = ControllerSite.objects.all()
      for ctrl_site in ctrl_sites:
          ctrls_by_site[ctrl_site.site].append(ctrl_site.controller)
      sites = Site.objects.all()
      for site in sites:
          if site not in ctrls_by_site or \
              controller not in ctrls_by_site[site]:
              controller_site = ControllerSite(controller=controller, site=site)
              controller_site.save()
      # relations for all slices
      ctrls_by_slice = defaultdict(list)
      ctrl_slices = ControllerSlice.objects.all()
      for ctrl_slice in ctrl_slices:
          ctrls_by_slice[ctrl_slice.slice].append(ctrl_slice.controller)
      slices = Slice.objects.all()
      for slice in slices:
          if slice not in ctrls_by_slice or \
              controller not in ctrls_by_slice:
              controller_slice = ControllerSlice(controller=controller, slice=slice)
              controller_slice.save()
      # relations for all users
      ctrls_by_user = defaultdict(list)
      ctrl_users = ControllerUser.objects.all()
      for ctrl_user in ctrl_users:
          ctrls_by_user[ctrl_user.user].append(ctrl_user.controller)
      users = User.objects.all()
      for user in users:
          if user not in ctrls_by_user or \
              controller not in ctrls_by_user[user]:
              controller_user = ControllerUser(controller=controller, user=user)
              controller_user.save()
      # relations for all networks
      ctrls_by_network = defaultdict(list)
      ctrl_networks = ControllerNetwork.objects.all()
      for ctrl_network in ctrl_networks:
          ctrls_by_network[ctrl_network.network].append(ctrl_network.controller)
      networks = Network.objects.all()
      for network in networks:
          if network not in ctrls_by_network or \
              controller not in ctrls_by_network[network]:
              controller_network = ControllerNetwork(controller=controller, network=network)
              controller_network.save()
      # relations for all images
      ctrls_by_image = defaultdict(list)
      ctrl_images = ControllerImages.objects.all()
      for ctrl_image in ctrl_images:
          ctrls_by_image[ctrl_image.image].append(ctrl_image.controller)
      images = Image.objects.all()
      for image in images:
          if image not in ctrls_by_image or \
              controller not in ctrls_by_image[image]:
              controller_image = ControllerImages(controller=controller, image=image)
              controller_image.save()
  
subject: Add images and networks to new controllers automatically through the controller model policies.