protected function after($key = null)
    {
        if (! $this->after) {
            $this->after = $this->parseData($this->activity->after);
        }

        if (! $key) {
            return array_keys($this->after);
        }

        if (! isset($this->after[$key]) || $this->after[$key] === '') {
            return null;
        }

        return $this->after[$key];
    }