Can factory provider have optional dependencies? : <p>For example:</p>

<pre><code>@NgModule ({
  providers: [ 
    { provide: MyService, 
      useFactory: (optionalDep) =&gt; new MyService(optionalDep)
      deps: [SOME_DEP]
    }
})
class MyModule {}
</code></pre>

<p>Can <strong>useFactory</strong> have optional dependencies? </p>
