/** 检查输入值是否为 'null' 或 'undefined'
 *
 * @example
 *
 *  isNil(null); //=> true
 *  isNil(undefined); //=> true
 *  isNil('0'); //=> false
 *  isNil([]); //=> false
 */
export declare function isNil(value: any): boolean;