import type { EventCallable } from "effector";
import type { OperationVariables } from "@apollo/client";
type EmptyVariables = Record<string, never>;
export type Optional<Payload> = Payload extends EmptyVariables ? void : Payload;
export declare function optional<Payload extends OperationVariables>(source: EventCallable<Payload>): EventCallable<Optional<Payload>>;
export {};