import { PipelineOperator } from "../../core";
/**
 * Populates null and missing field values within documents.
 *
 * See {@link https://www.mongodb.com/docs/manual/reference/operator/aggregation/fill/ usage}.
 *
 * @param collection
 * @param expr
 * @param options
 * @returns
 */
export declare const $fill: PipelineOperator;