{
  description = "Application packaged using poetry2nix";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable-small";
    # Added newest nixpkgs for an updated poetry package.
    nixpkgs-newest.url = "github:NixOS/nixpkgs/nixos-unstable";
    poetry2nix = {
      url = "github:nix-community/poetry2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs =
    {
      self,
      nixpkgs,
      flake-utils,
      poetry2nix,
      nixpkgs-newest,
    }:
    flake-utils.lib.eachDefaultSystem (
      system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        # Use the newest nixpkgs exclusively for the poetry package.
        pkgsNew = nixpkgs-newest.legacyPackages.${system};
        inherit (poetry2nix.lib.mkPoetry2Nix { inherit pkgs; }) mkPoetryApplication defaultPoetryOverrides;
        inherit poetry2nix;
      in
      {
        packages = {
          myapp = mkPoetryApplication {
            projectDir = self;
            preferWheels = true;
            overrides = defaultPoetryOverrides.extend (
              self: super: {
                umap = super.umap.overridePythonAttrs (old: {
                  buildInputs = (old.buildInputs or [ ]) ++ [ super.setuptools ];
                });
              }
            );
          };
          default = self.packages.${system}.myapp;
        };

        # Shell for app dependencies.
        #
        #     nix develop
        #
        # Use this shell for developing your app.
        devShells.default = pkgs.mkShell {
          inputsFrom = [
            self.packages.${system}.myapp
          ];
        };

        # Shell for poetry.
        #
        #     nix develop .#poetry
        #
        # Here we use the poetry package from the newest nixpkgs input while keeping
        # all other dependencies locked.
        devShells.poetry = pkgs.mkShell {
          packages = [ pkgsNew.poetry ];
        };
      }
    );
}