public function variables()
    {
        if (!$this->hasKeyword('STUB')) {
            return $this->keyword('HEADING')->values;
        } elseif (!$this->hasKeyword('HEADING')) {
            return $this->keyword('STUB')->values;
        } else {
            return array_merge($this->keyword('STUB')->values, $this->keyword('HEADING')->values);
        }
    }