*
   * <p><b>Note:</b> Double and single quotes are not escaped, so it is <b>not safe</b> to use this
   * escaper to escape attribute values. Use {@link #xmlContentEscaper} if the output can appear in
   * element content or {@link #xmlAttributeEscaper} in attribute values.
   *
   * <p>This escaper substitutes {@code 0xFFFD} for non-whitespace control characters and the

    //                                                                           Attribute
    //                                                                           =========

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========

    //                                                                           Attribute
    //                                                                           =========

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========

    protected FessFunctions() {
        // nothing
    }

    /**
     * Generates an HTML opening or closing tag with appropriate language attribute.
     *
     * @param isOpen true to generate opening HTML tag, false for closing tag
     * @return HTML opening tag with language attribute or closing tag
     */
    public static String html(final boolean isOpen) {
        if (isOpen) {

         * return null; }
         */
    }

    /**
     * Gets the reading from the attribute.
     * @param stream The token stream.
     * @return The reading from the attribute.
     */
    protected String getReadingFromAttribute(final TokenStream stream) {
        return null;
        /*

    //

    // ===================================================================================
    //                                                                           Attribute
    //

    // ===================================================================================
    //                                                                      Search Execute

    //

    // ===================================================================================
    //                                                                           Attribute
    //

    // ===================================================================================
    //                                                                      Search Execute

    //

    // ===================================================================================
    //                                                                           Attribute
    //

    // ===================================================================================
    //                                                                      Search Execute

    //

    // ===================================================================================
    //                                                                           Attribute
    //

    // ===================================================================================
    //                                                                      Search Execute

And these models are all sharing a lot of the data and duplicating attribute names and types.

We could do better.

We can declare a `UserBase` model that serves as a base for our other models. And then we can make subclasses of that model that inherit its attributes (type declarations, validation, etc).

All the data conversion, validation, documentation, etc. will still work as normally.