{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };
  outputs =
    {
      self,
      nixpkgs,
      flake-utils,
    }:
    flake-utils.lib.eachDefaultSystem (
      system:
      let
        pkgs = (import nixpkgs) {
          inherit system;
        };
      in
      rec {
        packages = rec {
          # also works on 3.15 but there are no packages easily available for that.
          python = pkgs.python314.overrideAttrs (
            finalAttrs: previousAttrs: {
              patches = previousAttrs.patches ++ [
                ./0001-add-to-parser.patch
              ];
              nativeBuildInputs = previousAttrs.nativeBuildInputs ++ [
                pkgs.python3
              ];
              postConfigure = ''
                ${previousAttrs.postConfigure or ""}
                make regen-pegen
                make regen-token
              '';
            }
          );
          default = python;
        };
        devShells.default =
          with pkgs;
          mkShell {
            buildInputs = [ ];
            packages = [
              packages.python
            ];
          };
      }
    );
}