hunk.code_window:       unsubscribe = () => source.off(eventName, handler);
       } else if (isNodeStyleEventEmmitter(sourceObj)) {
         const source = sourceObj;
         sourceObj.addListener(eventName, handler);
         unsubscribe = () => source.removeListener(eventName, handler);
       }
       subscriber.add(new Subscription(unsubscribe));
  
hunk.labels: keep keep keep keep add keep keep keep
hunk.after_edit:     } else {
         throw new TypeError('Invalid event target');
  
hunk.file_path: src/observable/FromEventObservable.ts
hunk.type: add
file: import { AnimationFrameAction } from './AnimationFrameAction';
  import { AnimationFrameScheduler } from './AnimationFrameScheduler';
  
  export const animationFrame = new AnimationFrameScheduler(AnimationFrameAction);
  