added flake for special plot script

tools/plot_scripts/background_ml_illustrations/flake.nix

@@ -0,0 +1,40 @@
+{
+  description = "Python 3.13 devshell with tensorflow-datasets, matplotlib, scikit-learn and numpy";
+
+  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;
+          # optional: config = { allowUnfree = true; };
+        };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          name = "py313-devshell";
+          # bring in the Python 3.13 packages
+          buildInputs =
+            with pkgs;
+            [ python313 ]
+            ++ (with pkgs.python313Packages; [
+              tensorflow-datasets
+              matplotlib
+              scikit-learn
+              numpy
+            ]);
+        };
+      }
+    );
+}