new_contents: from . import packet as p
  
  class Tracker:
      def __init__(self):
          self.objects = {}
  
      def update_object(self, record):
          try:
              oid = record['object']
          except KeyError:
              return
          else:
              self.objects.setdefault(oid, {}).update(record)
  
      def remove_object(self, oid):
          try:
              del self.objects[oid]
          except KeyError:
              pass
  
      def rx(self, packet):
          if isinstance(packet, p.ObjectUpdatePacket):
              for record in packet.records:
                  self.update_object(record)
          elif isinstance(packet, p.DestroyObjectPacket):
              self.remove_object(packet.object)
  
  
subject: Add a simple tracking mechanism