/**
     * Adds a rule for extracting child URLs from HTML tags.
     *
     * @param tagName the HTML tag name
     * @param attrName the attribute name to extract URLs from
     */
    public void addChildUrlRule(final String tagName, final String attrName) {
        if (StringUtil.isNotBlank(tagName) && StringUtil.isNotBlank(attrName)) {
            childUrlRuleMap.put(tagName, attrName);
        }
    }

    /**