/**
 * An implementation of Set that support first() and last() method.
 */
export declare class OrderedSet<T> {
    private set;
    private array;
    constructor();
    add(item: T): void;
    delete(item: T, searchFromHead: boolean): void;
    first(): T | null;
    last(): T | null;
    toArray(): T[];
    values(): IterableIterator<T>;
    has(item: T): boolean;
    get size(): number;
}
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