code: function(options) {
          // we'll want an option to supress notification here
          var layers = this.layers || [this.layer],
              layer, feature, l, numExcept;
          for(l=0; l<layers.length; ++l) {
              layer = layers[l];
              numExcept = 0;
              //layer.selectedFeatures is null when layer is destroyed and 
              //one of it's preremovelayer listener calls setLayer 
              //with another layer on this control
              if(layer.selectedFeatures != null) {
                  while(layer.selectedFeatures.length > numExcept) {
                      feature = layer.selectedFeatures[numExcept];
                      if(!options || options.except != feature) {
                          this.unselect(feature);
                      } else {
                          ++numExcept;
                      }
                  }
              }
          }
      }
docs: Method: unselectAll
  Unselect all selected features.  To unselect all except for a single
  feature, set the options.except property to the feature.
  
  Parameters:
  options - {Object} Optional configuration object.