code: def watcher():
      """Watcher task raises an AirflowException and is used to 'watch' tasks for failures
      and propagates fail status to the whole DAG Run"""
      raise AirflowException(
          "Failing task because one or more upstream tasks failed."
      )
  
imports: from __future__ import annotations
  from airflow.decorators import task
  from airflow.exceptions import AirflowException
  from airflow.utils.trigger_rule import TriggerRule
label_desc: Use image node_id 1 for calling a global function with example usage: watcher() without return types