import (
  builtins.fetchTarball {
    url = "https://github.com/nixos/nixpkgs/archive/a7bf8161fa834a602278c15fcbdd955656b3aed8.tar.gz";
    sha256 = "0lzd35niw0j8qy4mhglvqwv5qwyvdb9mhv8hpmn73ym57r92i4p1";
  }
)