code: function configureStyles(){
                          var _ = nvd3Utils.deepExtend(defaultStyles(), scope.options['styles'] || {});
  
                          if (scope._config.extended) scope.options['styles'] = _;
  
                          angular.forEach(_.classes, function(value, key){
                              value ? element.addClass(key) : element.removeClass(key);
                          });
  
                          element.removeAttr('style').css(_.css);
                      }
docs: Add some styles to the whole directive element