public function mime_parts()
    {
        if ($this->context === null) {
            return $this->mime_parts;
        }

        $parts = array();

        foreach ($this->mime_parts as $part_id => $part) {
            if ($this->check_context($part)) {
                $parts[$part_id] = $part;
            }
        }

        return $parts;
    }