import { AsyncSequence } from "../../sequency";
export declare class FirstOrNull {
    /**
     * Returns the first element of the sequence or the first element matching `predicate` if present, otherwise returns `null`.
     *
     * @param {(T) => Promise<boolean> | boolean} predicate
     * @returns {Promise<T | null>}
     */
    firstOrNull<T>(this: AsyncSequence<T>, predicate?: (item: T) => Promise<boolean> | boolean): Promise<T | null>;
    /**
     * Returns the first element of the sequence or the first element matching `predicate` if present, otherwise returns `null`.
     *
     * @param {(T) => Promise<boolean> | boolean} predicate
     * @returns {Promise<T | null>}
     */
    find<T>(this: AsyncSequence<T>, predicate?: (item: T) => Promise<boolean> | boolean): Promise<T | null>;
}