builtins.import
from Nixのbuiltin関数
https://nixos.org/guides/nix-pills/functions-and-imports.html#idm140737320492960
https://nix.dev/manual/nix/2.18/language/builtins#builtins-import
https://noogle.dev/f/builtins/import
.nixのfileを読み込む
import path/to/file {};