code: def get_dialogs_with_user(user_1, user_2):
      
      return Dialog.objects.filter(
          Q(owner=user_1, opponent=user_2) | Q(opponent=user_1, owner=user_2))
docs: gets the dialog between user_1 and user_2
      :param user_1: the first user in dialog (owner or opponent)
      :param user_2: the second user in dialog (owner or opponent)
      :return: queryset which include dialog between user_1 and user_2 (queryset can be empty)