Latte\Engine::addFilter PHP Method

    public function addFilter($name, $callback)
    {
        $this->filters->add($name, $callback);
        return $this;
    }

 public function register(Engine $engine)
 {
     if (class_exists('Latte\\Runtime\\FilterInfo')) {
         $engine->addFilter('translate', [$this, 'translateFilterAware']);
     } else {
         $engine->addFilter('translate', [$this, 'translate']);
     }
     $engine->addFilter('getTranslator', [$this, 'getTranslator']);
 }