export type Action<T> = {
    $set?: T;
    $unset?: true;
    $push?: T;
    $addToSet?: T;
};
export declare namespace Action {
    function is(value: any | Action<any>): value is Action<any>;
    type Operator = "$set" | "$unset" | "$push" | "$addToSet";
    namespace Operator {
        function is(value: any | Operator): value is Operator;
    }
    function extract<T>(action: Action<T> | any): Action<T> | undefined;
}