/**
 * Describes how a CollectionView groups items on one property. The optional
 * `converter` turns a raw cell value into a group key, so callers can group
 * dates by year or numbers into ranges instead of by exact value.
 */
export declare class PropertyGroupDescription<T = Record<string, unknown>> {
    readonly property: string;
    private readonly converter?;
    constructor(property: string, converter?: ((item: T, value: unknown) => unknown) | undefined);
    /** The key an item belongs under. Items with equal keys share a group. */
    groupKey(item: T): unknown;
}