Why does this example require Observable when it's not used?

On this page:

How come the Observable is required in but explicitly NOT used?

Is there some type of implicit “magic” going on?

That particular example does not need the require(). It should be removed from there.

Unrelated to the require(), there is some implicit magic going on - all properties passed to components are implicitly available as derived Observables in JavaScript as this.varName.