import (fetchTarball {
  url = "https://github.com/NixOS/nixpkgs/archive/31c38894c90429c9554eab1b416e59e3b6e054df.tar.gz";
  sha256 = "1fv14rj5zslzm14ak4lvwqix94gm18h28376h4hsmrqqpnfqwsdw";
})