assertArgumentNotNull("children", children);
        assertArgumentNotNull("buf", buf);

        final int length = children.getLength();
        for (int i = 0; i < length; ++i) {
            appendNode(children.item(i), buf);
        }
    }

    /**
     * Appends the string representation of a {@link NamedNodeMap}.
     *
     * @param attrs