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of(...items): Returns an Observable instance that synchronously delivers the
values provided as arguments.

Example:
// Create simple observable that emits three values
const myObservable = of(1, 2, 3);

// Create observer object
const myObserver = {
  next: (x: number) => console.log('Observer got a next value: ' + x),
  error: (err: Error) => console.error('Observer got an error: ' + err),
  complete: () => console.log('Observer got a complete notification'),
};

// Execute with the observer object
myObservable.subscribe(myObserver);

// Logs:
// Observer got a next value: 1
// Observer got a next value: 2
// Observer got a next value: 3
// Observer got a complete notification
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