docs: function initProperties() {
      var that = this;
  
      that.options = {};
      that.container = null;
      that.showTransitionStartAnimation = null;
      that.showTransitionEndTimeout = null;
      that.hideTransitionStartAnimation = null;
      that.hideTransitionEndTimeout = null;
      that.showing = false;
      that.hiding = false;
      that.hidden = false;
  
      return that;
    }