protected function addTwigFunction($name, $callback, $options = [])
    {
        // If we pass a callback as a simple string, we need to turn it into an array.
        if (is_string($callback) && method_exists($this, $callback)) {
            $callback = [$this, $callback];
        }

        $safe = method_exists($this, 'isSafe') && $this->isSafe();
        if (isset($options['safe'])) {
            $safe = (bool) $options['safe'];
            unset($options['safe']);
        }

        $this->twigFunctions[] = new TwigFunction($name, $callback, $options);

        if ($safe) {
            $this->safeFunctionNames[] = $name;
        }
    }