My flake:

{
 description = "";

 inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
 inputs.flake-utils.url = "github:numtide/flake-utils";

 outputs = { self, nixpkgs, flake-utils, ... }:
    flake-utils.lib.eachDefaultSystem (system: let
      pkgs = nixpkgs.legacyPackages.${system};
      
    
        # propagatedBuildInputs = [
            
        #   ];
      mesop = with pkgs.python3Packages;
        buildPythonPackage rec {
        pname = "mesop";
        version = "0.8.0";
        format = "wheel";
        src = pkgs.python3Packages.fetchPypi rec {
            inherit pname version format;
            sha256 = "f156bf53f672588339b2be461017aecda860b9ffca15c86553f76255dd882670";
            dist = python;
        python = "py3";
        };

          # Convert line endings to Unix-style
          preConfigure = ''
          '';
             # put this code inside preConfigure if you want to run it dos2unix -f /nix/store/v099hqvw5z87423p4hz1vfhzaqa07dii-stdenv-linux/setup
        };
   
      pythonEnv = pkgs:
        pkgs.python3.withPackages (ps:
          with ps; [
             mesop
             absl-py 
             flask
             google
          ]);
    in {
      devShells.default = pkgs.mkShell {
        buildInputs = with pkgs; [
          curl
          (pythonEnv pkgs)
        ];
      };
    });
}

I need the google package (https://search.nixos.org/packages?channel=unstable&from=0&size=50&sort=relevance&type=packages&query=google )to use the command mesop. I added it. I ran the flake successfully.

  nix develop

But when I tried to run the command mesop.

   mesop

I got this problem:

Traceback (most recent call last):
File “/nix/store/2f1faid63zawdgnmg7hn51mqwndn8gkk-python3.11-mesop-0.8.0/bin/.mesop-wrapped”, line 6, in
from mesop.bin.bin import run_main
File “/nix/store/ywsz5bbhkfgb0lh4xyxhpsc731c8labg-python3-3.11.9-env/lib/python3.11/site-packages/mesop/init.py”, line 5, in
from mesop.colab.colab_run import colab_run as colab_run
File “/nix/store/ywsz5bbhkfgb0lh4xyxhpsc731c8labg-python3-3.11.9-env/lib/python3.11/site-packages/mesop/colab/colab_run.py”, line 6, in
from mesop.runtime import enable_debug_mode
File “/nix/store/ywsz5bbhkfgb0lh4xyxhpsc731c8labg-python3-3.11.9-env/lib/python3.11/site-packages/mesop/runtime/init.py”, line 1, in
from .runtime import (
File “/nix/store/ywsz5bbhkfgb0lh4xyxhpsc731c8labg-python3-3.11.9-env/lib/python3.11/site-packages/mesop/runtime/runtime.py”, line 6, in
import mesop.protos.ui_pb2 as pb
File “/nix/store/ywsz5bbhkfgb0lh4xyxhpsc731c8labg-python3-3.11.9-env/lib/python3.11/site-packages/mesop/protos/ui_pb2.py”, line 5, in
from google.protobuf.internal import builder as _builder
ModuleNotFoundError: No module named ‘google’