     @enum {string}
   ###
   @CSS:
-    BUTTON_TAG: 'li',
-    BUTTON_CLASS: 'dropup-button',
-    TARGET_ATTRIBUTE: 'target',
-    CARET: 'caret-marker', # do not set to 'caret', as it is would add another arrow
-    ARROW_UP: 'fa-angle-up',
+    BUTTON_TAG: 'li'
+    BUTTON_CLASS: 'dropup-button'
+    TARGET_ATTRIBUTE: 'target'
+    CARET: 'caret-marker' # do not set to 'caret', as it is would add another arrow
+    ARROW_UP: 'fa-angle-up'
     ARROW_LEFT: 'fa-angle-left'
+    COLLAPSE: 'collapse'
 
   ###
     @enum {number}

    animates dopupElement into opened position
  ###
  open: ->
    goog.style.setElementShown @dropupElement, true
    animation = @getAnimation(0, @height)

    animation.listen goog.fx.Animation.EventType.FINISH, (event) =>


    animation.listen goog.fx.Animation.EventType.FINISH, (event) =>
      goog.style.setElementShown @dropupElement, false
      goog.dom.classes.add @dropupElement, wzk.ui.dropup.Dropup.CSS.COLLAPSE
      @swapClasses()

    animation.play()
