setHTML(html) {
        const me = this,
            container = me._container;

        me._html = html;
        if (container) {
            container.querySelector('#panel-content').innerHTML = html;
        }

        return me;
    }
Sets the panel's content to the HTML provided as a string.
@param {string} html - A string representing HTML content for the panel
@returns {Panel} Returns itself to allow for method chaining