Weird error in shell exec not found

I’m trying to install a library (faunadb) with pip but i keep getting an error in the console.
The error says: line 3: exec: : not found

this happens because of some error in the nix file that stops it from being loaded → $PYTHONBIN isn’t set → it expands to nothing in the python3 script → blank argument to exec. Try to fix any errors in the nix file and send a link to your repl if stuck

Thanks for responding,
I checked the .nix file and this is the content:
{ pkgs }: { deps = [ pkgs.python3 run pkgs.python38Full ]; env = { PYTHON_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [ # Needed for pandas / numpy pkgs.zlib # Needed for pygame pkgs.glib # Needed for matplotlib pkgs.xorg.libX11 ]; PYTHONBIN = "${pkgs.python38Full}/bin/python3.8"; LANG = "en_US.UTF-8"; }; }
Also, whenever I do anything in the shell, I get this message:
error: undefined variable ‘run’ at /home/runner/Flask-Login-Test/replit.nix:3:18
This is the repl:

remove pkgs.python3 run