anchor.diff:    @Input()
     bool shouldExpandAllWhenFiltered = true;
   
  +  /// Function to convert the selected value to a string to be displayed as the
  +  /// button text.
  +  @Input()
  +  ItemRenderer labelRenderer;
  +
     bool get showFilterInsideButton =>
         supportsFiltering && !showFilterInsidePopup;
   
     Filterable get filterableOptions => options is Filterable
         ? options as Filterable
         : throw StateError(
  -          'The SlectionOptions provided should implement Filterable');
  +          'The SelectionOptions provided should implement Filterable');
   
     bool get expandAll =>
         _expandAll || (isFiltered && shouldExpandAllWhenFiltered);
   
  +  /// Returns the text to be displayed in the button or in the filter (if
  +  /// enabled).
  +  ///
  +  /// If a value has been selected for a single-select dropdown, this will
  +  /// render the selected value with [labelRenderer], [itemRenderer], or
  +  /// [defaultItemRenderer] in that order of preference.
     String get placeholder {
       if (selection is! MultiSelectionModel && selection.isNotEmpty) {
  -      return (itemRenderer ??
  -          defaultItemRenderer)(selection.selectedValues.first);
  +      return (labelRenderer ?? (itemRenderer ?? defaultItemRenderer))(
  +          selection.selectedValues.first);
       }
       return _placeholder;
     }
  
positive.code:   String _placeholder = _DEFAULT_PLACEHOLDER;
    bool _visible = false;
    List<RelativePosition> _customPopupPositions;
  
    @ViewChild(MaterialTreeFilterComponent)
    MaterialTreeFilterComponent materialTreeFilterComponent;
  
negative.code: import 'package:angular_components/model/selection/selection_container.dart';
  import 'package:angular_components/model/selection/selection_model.dart';
  import 'package:angular_components/model/selection/selection_options.dart';
  import 'package:angular_components/model/ui/has_factory.dart';
  import 'package:angular_components/model/ui/has_renderer.dart';
  import 'package:angular_components/utils/browser/dom_service/dom_service.dart';
  
  import 'material_tree_impl.dart';
  