/**
 * @param x
 * @return {x is Function}
 */
export function isFunction(x: any): x is Function;
/**
 * @param x
 * @return {x is string}
 */
export function isString(x: any): x is string;
/**
 * @param x
 * @return {x is undefined}
 */
export function isUndefined(x: any): x is undefined;
/**
 * @param x
 * @return {x is boolean}
 */
export function isBoolean(x: any): x is boolean;
/**
 * @template T
 * @param x
 * @return {x is Array<T>}
 */
export function isArray<T>(x: any): x is T[];
/**
 * @param obj
 * @return {obj is Object}
 */
export function isObject(obj: any): obj is Object;