src/ObservableTrait.php
function off(string $event, $callback): bool
    {
        return $this->getEventEmitter()->off($event, $callback);
    }
function off(string $event, $callback): bool
    {
        return $this->getEventEmitter()->off($event, $callback);
    }
function off ( string $ event , $ callback ) : bool { return $ this -> getEventEmitter ( ) -> off ( $ event , $ callback ) ; }
Unregister a callback
Unregister a callback