https://wikidocs.net/44249 https://ashhyun.github.io/%EB%A8%B8%EC%8B%A0%EB%9F%AC%EB%8B%9D/ML_splitting_dataset/ https://velog.io/@ljs7463/%EB%A8%B8%EC%8B%A0%EB%9F%AC%EB%8B%9D-%ED%95%99%EC%8A%B5%EC%9D%84-%EC%9C%84%ED%95%9C-%EB%8D%B0%EC%9D%B4%ED%84%B0%EC%85%8B-%EB%B6%84%EB%A6%ACtraintestvalidation
