import { PipelineOperator } from "../../core";
/**
 * Reshapes each document in the stream, such as by adding new fields or removing existing fields.
 * For each input document, outputs one document.
 *
 * See {@link https://www.mongodb.com/docs/manual/reference/operator/aggregation/project usage}.
 *
 * @param collection
 * @param expr
 * @param opt
 * @returns
 */
export declare const $project: PipelineOperator;