code: function () {
  
              if (!this.shouldOpen()) return false;
  
              this.opening();
  
              // Only bind the document mousemove when the dropdown is visible
              $document.on("mousemove.select2Event", function (e) {
                  lastMousePosition.x = e.pageX;
                  lastMousePosition.y = e.pageY;
              });
  
              return true;
          }
docs: Opens the dropdown
  
  @return {Boolean} whether or not dropdown was opened. This method will return false if, for example,
  the dropdown is already open, or if the 'open' event listener on the element called preventDefault().
   abstract