anchor.diff:  , buildPythonPackage
   , fetchFromGitHub
   # , cplex
  -, cvxopt
  +, cvxpy
   , dlx
   , docplex
   , fastdtw
  
positive.code:     owner = "Qiskit";
      repo = "qiskit-aqua";
      rev = version;
      sha256 = "0yykw6k1rb3f2ihcp0y9pb0695mcmy29nyqlj89qs4da0503vxvh";
    };
  
    # Optional packages: pyscf (see below NOTE) & pytorch. Can install via pip/nix if needed.
    propagatedBuildInputs = [
      # cplex
      cvxopt
      docplex
      dlx # Python Dancing Links package
      fastdtw
  
negative.code:         "You must install it yourself via pip or add it to your environment from the Nix User Repository." \
          "', ImportWarning)\n" \
        >> qiskit/optimization/__init__.py
    '';
  
    postInstall = "rm -rf $out/${python.sitePackages}/docs";  # Remove docs dir b/c it can cause conflicts.
  