import { Iterator } from "../../lazy";
import { Any, AnyObject, Options } from "../../types";
interface InputExpr {
    groupBy: Any;
    boundaries: Any[];
    default: Any;
    output?: AnyObject;
}
/**
 * Categorizes incoming documents into groups, called buckets, based on a specified
 * expression and bucket boundaries and outputs a document per each bucket.
 *
 * See {@link https://docs.mongodb.com/manual/reference/operator/aggregation/bucket/ usage}.
 */
export declare function $bucket(coll: Iterator, expr: InputExpr, options: Options): Iterator;
export {};