Invisible block

When in need of a moodle-ish way (as of v1.9.x; in v2.x we got local) to install a non-visible piece of code or in other name a library, we can just use a block and override the user_can_addto method this way:

public function user_can_addto(&$page)
    return false
}

This way we can have all the bendfits that comes with a block, except the unwanted feature of a block as visual component.