**NEVER** use emoji, or unicode that emulates emoji (e.g. ✓, ✗).
First: mockToString — The Lie That Defeats The Check
，这一点在im钱包官方下载中也有详细论述
// 栈空 → 无更大元素，返回-1；栈非空 → 取栈顶（第一个更大值）
1) What is an NFT?NFT stands for non-fungible token, which is a cryptographic token on a blockchain with unique identification codes that distinguish it from other tokens. NFTs are unique and not interchangeable, which means no two NFTs are the same. NFTs can be a unique artwork, GIF, Images, videos, Audio album. in-game items, collectibles etc.