anchor.diff:    passthru = {
       pdf_sets = import ./pdf_sets.nix { inherit stdenv fetchurl; };
     };
  +
  +  postInstall = ''
  +    wrapProgram $out/bin/lhapdf --prefix PYTHONPATH : "$(toPythonPath "$out")"
  +  '';
   
     meta = {
       description = "A general purpose interpolator, used for evaluating Parton Distribution Functions from discretised data files";
  
positive.code: { stdenv, fetchurl, python2 }:
  
  stdenv.mkDerivation rec {
    name = "lhapdf-${version}";
  
negative.code:     sha256 = "0bi02xcmq5as0wf0jn6i3hx0qy0hj61m02sbrbzd1gwjhpccwmvd";
    };
  
    nativeBuildInputs = [ makeWrapper ];
    buildInputs = [ python2 ];
  
    enableParallelBuilding = true;
  