I couldn't find any official documentation specifying what each parameter to a `sla_miss_callback` callable are. This would be a great addition to know how to properly format the messages sent.
airflow/models/dag.py
tis = tis.filter(or_(*conditions))
        else:
            tis = tis.filter(TaskInstance.dag_id == self.dag_id, TaskInstance.task_id.in_(self.task_ids))
        if run_id:
            tis = tis.filter(TaskInstance.run_id == run_id)
        if start_date:
            tis = tis.filter(DagRun.execution_date >= start_date)
        if task_ids:
            tis = tis.filter(TaskInstance.task_id.in_(task_ids))
        
        if end_date or not self.allow_future_exec_dates:
            end_date = end_date or timezone.utcnow()
            tis = tis.filter(DagRun.execution_date <= end_date)
        if state:
            if isinstance(state, str):
                tis = tis.filter(TaskInstance.state == state)
            elif len(state) == 1:
                tis = tis.filter(TaskInstance.state == state[0])
            else:
                
                if None in state:
                    if all(x is None for x in state):
                        tis = tis.filter(TaskInstance.state.is_(None))
                    else:
                        not_none_state = [s for s in state if s]
                        tis = tis.filter(
                            or_(TaskInstance.state.in_(not_none_state), TaskInstance.state.is_(None))
                        )
                else:
                    tis = tis.filter(TaskInstance.state.in_(state))