1. BackgroundAs NFT is becoming a dominant part of the crypto world, there emerged a large number of NFTs in different types and styles, such as collectibles, art NFTs, in-game assets, lands of virtual world and various utilities. Meanwhile, the market value of NFT has also risen, and as of press time, the total market value of NFT has also reached $21.15 billion, slowly showing the financial attributes of NFT.Marketcap and Trading Volume of NFT (source: nftgo.io)Unlike traditional ERC-20 Tok...