code: function(callback) {
  
              var self = this,
                  showEffect = self.options["showEffect"],
                  showEffectSpeed = self.options["showEffectSpeed"],
                  showEffectOptions = self.options["showEffectOptions"],
                  isNative = self.options["native"],
                  isMobile = self.isMobile;
  
              // If there are no select box options, do not try to open the select box
              if(!self.listItems.length || self.dropdown.hasClass(self.theme["disabled"])) {
  
                  return self;
  
              }
  
              // If the new drop down is being used and is not visible
              if((!isNative && !isMobile) && !this.list.is(":visible")) {
  
                  // Triggers a custom "open" event on the original select box
                  self.triggerEvent("open");
  
                  if (self._dynamicPositioning && self.options["dynamicPositioning"]) {
  
                      // Dynamically positions the dropdown list options list
                      self._dynamicPositioning();
  
                  }
  
                  // Uses `no effect`
                  if(showEffect === "none") {
  
                      // Does not require a callback function because this animation will complete before the call to `scrollToView`
                      self.list.show();
  
                  }
  
                  // Uses the jQuery `show` special effect
                  else if(showEffect === "show" || showEffect === "slideDown" || showEffect === "fadeIn") {
  
                      // Requires a callback function to determine when the `show` animation is complete
                      self.list[showEffect](showEffectSpeed);
  
                  }
  
                  // If none of the above options were passed, then a `jqueryUI show effect` is expected
                  else {
  
                      // Allows for custom show effects via the [jQueryUI core effects](http://http://jqueryui.com/demos/show/)
                      self.list.show(showEffect, showEffectOptions, showEffectSpeed);
  
                  }
  
                  self.list.promise().done(function() {
  
                      // Updates the list `scrollTop` attribute
                      self._scrollToView("search");
  
                      // Triggers a custom "opened" event when the drop down list is done animating
                      self.triggerEvent("opened");
  
                  });
  
              }
  
              // Provide callback function support
              self._callbackSupport(callback);
  
              // Maintains chainability
              return self;
  
          }
docs: Open ---- Opens the dropdown list options list