code: def test_get_subscribers():
      observer = SimpleObserver()
      observable = Observable(events=EVENTS)
      observable.subscribe("a", observer)
  
      assert observer in observable.get_subscribers("a")
      assert observer not in observable.get_subscribers("b")
      assert observer not in observable.get_subscribers("c")
  
      assert len(observable.get_subscribers("a")) == 1
      assert len(observable.get_subscribers("b")) == 0
      assert len(observable.get_subscribers("c")) == 0
  
file_path: BayesianOptimization/tests/test_observer.py
imports: from bayes_opt.bayesian_optimization import Observable
  from bayes_opt.observer import _Tracker
  from bayes_opt.event import Events
  import os
label_desc: Use image node_id 1 for calling a global function with example usage: test_get_subscribers() without return types