How to create an overlay for a python package in a flake

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EDIT: I figured it out and the flakes below are working.

…

I have packaged a python package called firedrake. This package relies on another python package I wrote called recursivenodes. My goal is to create an overlay of nixpkgs with firedrake in it, and then use it in a devShell.

The directory structure of where I created the overlay and packaged firedrake looks like this:

.
├── flake.nix
├── pkgs
   ├── firedrake
      ├── default.nix
   ├── recursivenodes
      ├── default.nix

The flake.nix file currently looks like this

{
  description = "Overlay flake";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
  };

  outputs =
    { self, nixpkgs,  ... }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
      };
    in
    {
 
      overlays.default = final: prev: rec {

        pythonPackagesOverlays = (prev.pythonPackagesOverlays or [ ]) ++ [
          (python-final: python-prev: rec { 
            recursivenodes = pkgs.python3Packages.callPackage ./pkgs/recursivenodes { };
            firedrake = prev.python3Packages.callPackage ./pkgs/firedrake { inherit recursivenodes; }; 
          })
        ];
      
        python3 =
          let
            self = prev.python3.override {
              inherit self;
              packageOverrides = prev.lib.composeManyExtensions final.pythonPackagesOverlays;
            }; in
          self;

  python3Packages = final.python3.pkgs;
      };

}

The above flake lives in a github repo at github:megaloblasto/custom-nixpkgs.

Then, my goal is to consume this overlay in a separate flake like this:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    custom-nixpkgs.url = "github:megaloblasto/custom-nixpkgs";
  };

  outputs =
    { self, nixpkgs, custom-nixpkgs, ... }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
        overlays = [ custom-nixpkgs.overlays.python ];
      };
    in
    {
      devShells.${system}.default = pkgs.mkShell {
        packages = [
          # Here is where firedrake is called
          (pkgs.python3.withPackages (python-pkgs: [
            python-pkgs.firedrake
          ]))
        ];
      };
   };
}