code: function(callback) {
  
              var self = this;
  
              // Checks to make sure the parameter passed in is a function
              if ($.isFunction(callback)) {
  
                  // Calls the method passed in as a parameter and sets the current `SelectBoxIt` object that is stored in the jQuery data method as the context(allows for `this` to reference the SelectBoxIt API Methods in the callback function. The `dropdown` DOM element that acts as the new dropdown list is also passed as the only parameter to the callback
                  callback.call(self, self.dropdown);
  
              }
  
              // Maintains chainability
              return self;
  
          }
docs: _Callback --------- Call the function passed into the method