anchor.diff:      NgFor,
       NgIf
     ],
  -  host: const {
  -    '[attr.role]': 'role',
  -    // Unable to use interpolation for aria-multiselectable and aria-readonly
  -    // due to https://github.com/angular/angular/issues/3583
  -    '[attr.aria-multiselectable]': 'showFlatCheck ? "true" : "false"',
  -    '[attr.aria-readonly]': 'showFlatList ? "true" : "false"',
  -  },
     viewProviders: const [
       const Provider(MaterialTreeRoot, useExisting: MaterialTreeComponent)
     ],
  
positive.code:       return "list";
      }
    }
  }
  
negative.code:   bool get showFlatRadio => !showFlatList && !showFlatCheck;
  
    /// The ARIA role to use for the host element.
    @HostBinding('attr.role')
    String get role {
      if (supportsHierarchy) {
        return "tree";
  