{
  inputs.flake-utils.url = "github:numtide/flake-utils";
  outputs = { self, flake-utils, nixpkgs }:
    flake-utils.lib.eachSystem [ "x86_64-linux" ] (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        pythonPkgs = pkgs.python39Packages;
        flakePkgs = rec {
          material = pkgs.callPackage ./material {};
          sm2 = pythonPkgs.callPackage ./sm2 {};
        };
      in rec {
        defaultPackage = packages.sm2;
        devShell = pkgs.mkShell {
          packages = with pkgs; [
            (python39.withPackages (p: with p; [
              flask
            ]))
          ];
        };
        packages = flake-utils.lib.flattenTree flakePkgs;
      });
}