def get_dialog_between_users(user1_id, user2_id):
    qs = ParticipantChat.objects.filter(chat__is_group=False)

    chats_user1 = qs.filter(user__id=user1_id).values_list('chat_id', flat=True)
    chats_user2 = qs.filter(user__id=user2_id).values_list('chat_id', flat=True)

    dialog_ids = set(chats_user1) & set(chats_user2)

    if len(dialog_ids) > 1:
        raise exceptions.ValidationError(detail='There is more than one chat between users')
    if not dialog_ids:
        return None

    dialog_id = dialog_ids.pop()
    return Chat.objects.filter(id=dialog_id).first()