While doing the tutorial of "Build the Substrate Kitties Chain" there comes a section https://docs.substrate.io/tutorials/v3/kitties/pt1/#uniqueness-custom-types-and-storage-maps
In this there it says 'Along with this code, we'll need to import serde. Add this to your pallet's Cargo.toml file, using the matching version as Substrate upstream.'
So How to add serde in cargo.toml?