import { Iterator } from "../../lazy";
import { Any, Options, SortSpec } from "../../types";
type Output = [{
    value: Any;
}, {
    method: "linear" | "locf";
}];
interface InputExpr {
    partitionBy?: Any;
    partitionByFields?: string[];
    sortBy?: SortSpec;
    output: Record<string, Output[number]>;
}
/**
 * Populates null and missing field values within documents.
 *
 * See {@link https://www.mongodb.com/docs/manual/reference/operator/aggregation/fill/ usage}.
 */
export declare function $fill(coll: Iterator, expr: InputExpr, options: Options): Iterator;
export {};