export declare function isEvent(candidate: unknown): candidate is Event; export declare function isPlainObject(candidate: unknown): candidate is Record; export declare function isInstanceOf(candidate: unknown, base: any): boolean; export declare function isPrimitive(candidate: unknown): candidate is number | string | boolean | bigint | symbol | null | undefined; export declare function isError(candidate: unknown): candidate is Error; export declare function isErrorEvent(event: string | Error | Event): event is ErrorEvent; export declare function isErrorWithStack(candidate: unknown): candidate is Error; export declare function isBuiltin(candidate: unknown, className: string): boolean; export declare function isDOMException(candidate: unknown): boolean; export declare function isDOMError(candidate: unknown): boolean;