code: async def save(self):
          
          if 'vlan' in self._changed_data and self._changed_data['vlan']:
              # Update uses the ID of the VLAN, not the VLAN object.
              self._changed_data['vlan'] = self._changed_data['vlan']['id']
              if (self._orig_data['vlan'] and
                      'id' in self._orig_data['vlan'] and
                      self._changed_data['vlan'] == (
                          self._orig_data['vlan']['id'])):
                  # VLAN didn't really change, the object was just set to the
                  # same VLAN.
                  del self._changed_data['vlan']
          await super(Subnet, self).save()
docs: Save this subnet.