import { TreeMeta } from './core-tree-engine';
export declare class CoreTreeStateService<T extends TreeMeta> {
    private parentMap;
    flatTree: import("@angular/core").WritableSignal<T[]>;
    expandedKeys: import("@angular/core").WritableSignal<Set<string>>;
    setData(items: T[]): void;
    toggle(id: string): void;
    visibleItems: import("@angular/core").Signal<T[]>;
}