public function getShapeDocs($shapeName, $parentName, $ref)
    {
        if (!isset($this->docs['shapes'][$shapeName])) {
            return '';
        }

        $result = '';
        $d = $this->docs['shapes'][$shapeName];
        if (isset($d['refs']["{$parentName}\$${ref}"])) {
            $result = $d['refs']["{$parentName}\$${ref}"];
        } elseif (isset($d['base'])) {
            $result = $d['base'];
        }

        if (isset($d['append'])) {
            $result .= $d['append'];
        }

        return $this->clean($result);
    }