overrideCoreByPackage view.php

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Hello,
I'm using Concrete5 v.5.6.
I need to create a package that add some methods to the "libraries/view.php" class.

Inside the controller package I've written the following code:
public function on_start() {
      $objEnv = Environment::get();
      $objEnv->overrideCoreByPackage('libraries/view.php', $this);
}

But is not working...

The "view.php" file works only if I put it inside the top-level "libraries" directory.
Someone can help me?

Thanks you very much!