block8.from

django.contrib.contenttypes.models  import  ContentType
from  django.db.models  import  Value
from  itertools  import  chain

@property
def messages(self):
  from conversation.models import Message
  message_type = ContentType.objects.get_for_model(self)
  msgFromLead = Message.objects.filter(sender_id=self.id, sender_type=message_type).annotate(
      from_lead=Value(True, models.BooleanField())
  )

  msgToLead =  Message.objects.filter(receiver_id=self.id, receiver_type=message_type).annotate(
      from_lead=Value(False, models.BooleanField())
  )
  messages = sorted(
      chain(msgFromLead, msgToLead), 
      key=lambda instance: instance.date_created
  )

  return messages