$ cat flake.nix
{
  description = "Application packaged using poetry2nix";

  inputs.flake-utils.url = "github:numtide/flake-utils";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs";
  inputs.poetry2nix.url = "github:nix-community/poetry2nix";

  outputs = { self, nixpkgs, flake-utils, poetry2nix }:
    {
      # Nixpkgs overlay providing the application
      overlay = nixpkgs.lib.composeManyExtensions [
        poetry2nix.overlay
        (final: prev: {
          # The application
          myapp = prev.poetry2nix.mkPoetryApplication {
            projectDir = ./.;
          };
          myenv = prev.poetry2nix.mkPoetryEnv {
            projectDir = ./.;
          };
        })
      ];
    } // (flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          overlays = [ self.overlay ];
        };
      in
      rec {
        apps = {
          myapp = pkgs.myapp;
        };

        devShell = pkgs.myenv;
        defaultApp = apps.myapp;
      }));
}

$ cat poetry.toml
[[package]]
name = "sly"
version = "0.4"
description = "SLY - Sly Lex Yacc"
category = "main"
optional = false
python-versions = "*"

[package.extras]
test = ["pytest", "regex"]

[metadata]
lock-version = "1.1"
python-versions = "^3.8"
content-hash = "848dc9cdd8c412a60674d1709c1e95a9f70d16c69c8ab0e918d3cc05d64249e5"

[metadata.files]
sly = [
    {file = "sly-0.4.tar.gz", hash = "sha256:e5f2266a231322cc17519fbc3a3ba1c6335fed5a9a55abe0e598a35aea0ac32a"},
]