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