メモリ管理
https://zenn.dev/shimakaze_soft/scraps/b1d42a2b13ab8d
https://docs.python.org/ja/3/library/gc.html
https://dtnavi.tcdigital.jp/cat_system/language_202/
https://qiita.com/Tadataka_Takahashi/items/a5d9654bba38d4eb3686