public function getFunctions()
    {
        return [
            new \Twig_SimpleFunction(
                'variable',
                function ($group, $field) {
                    return $this->dispatch(new GetValuePresenter($group, $field));
                }
            ),
            new \Twig_SimpleFunction(
                'variable_value',
                function ($group, $field, $default = null) {
                    return $this->dispatch(new GetVariableValue($group, $field, $default));
                }
            ),
            new \Twig_SimpleFunction(
                'variable_group',
                function ($group) {
                    return (new Decorator())->decorate($this->dispatch(new GetVariableGroup($group)));
                }
            ),
        ];
    }