/**
 * 深层映射对象键
 * @template T
 * @param {T} obj - 要转换键名的对象
 * @param {(key: string) => string} fn - 键名转换函数
 * @returns {T} - 转换后的新对象
 * @example
 *
 * const obj = {
 *   foo: '1',
 *   nested: {
 *     child: {
 *       withArray: [
 *         {
 *           grandChild: ['hello']
 *         }
 *       ]
 *     }
 *   }
 * };
 *
 * const upperKeysObj = deepMapKeys(obj, key => key.toUpperCase());
 * // =>
 * {
 *   "FOO":"1",
 *   "NESTED":{
 *     "CHILD":{
 *       "WITHARRAY":[
 *         {
 *           "GRANDCHILD":[ 'hello' ]
 *         }
 *       ]
 *     }
 *   }
 * }
 */
export declare function deepMapKeys<T extends Record<string, any>>(obj: T, fn: (key: string) => string): T;