public function filter_text($text, $context, array $options = array(),
            array $skipfilters = null) {
        $text = $this->apply_filter_chain($text, $this->get_text_filters($context), $options, $skipfilters);
        // Remove <nolink> tags for XHTML compatibility.
        $text = str_replace(array('<nolink>', '</nolink>'), '', $text);
        return $text;
    }