export declare function isBoolean(arg: unknown): arg is boolean;
export declare function isString(arg: unknown): arg is string;
export declare function isNumber(arg: unknown): arg is number;
export declare function isFunction(arg: unknown): arg is (...args: unknown[]) => unknown;
export declare function isObject(arg: unknown): arg is object;
export declare function isArray<T>(arg: unknown): arg is T[];
export declare function isNull(arg: unknown): arg is null | undefined;