code: def test_run_observer():
      # basically to silence coverage
      r = RunObserver()
      assert (
          r.started_event(
              {}, "run", {}, datetime.utcnow(), {}, "comment", None
          )
          is None
      )
      assert (
          r.heartbeat_event({}, "", datetime.utcnow(), "result") is None
      )
      assert r.completed_event(datetime.utcnow(), 123) is None
      assert (
          r.interrupted_event(datetime.utcnow(), "INTERRUPTED") is None
      )
      assert r.failed_event(datetime.utcnow(), "trace") is None
      assert r.artifact_event("foo", "foo.txt") is None
      assert r.resource_event("foo.txt") is None
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_run_observer() without return types