anchor.diff:    # nixpkgs.
     buildInputs = [
       boost
  +    cereal
       curl
       expat
       glew
  
positive.code:   src = fetchFromGitHub {
      owner = "prusa3d";
      repo = "PrusaSlicer";
      sha256 = "135wn2sza2f2kvbja1haxil5kx1b74lc1i7dsa35i1y3phabykhz";
      rev = "version_${version}";
    };
  
  
negative.code: { stdenv, lib, fetchFromGitHub, makeWrapper, cmake, pkgconfig
  , boost, cereal, curl, expat, glew, libpng, tbb, wxGTK30
  , gtest, nlopt, xorg, makeDesktopItem
  }:
  let
  