anchor.diff:  , buildPythonPackage
   , fetchFromGitHub
   , cmake
  +, boost
   , eigen
   , python
   , catch
  
positive.code:   dontUseCmakeBuildDir = true;
  
    cmakeFlags = [
      "-DEIGEN3_INCLUDE_DIR=${eigen}/include/eigen3"
      "-DBUILD_TESTING=on"
    ] ++ lib.optionals (python.isPy3k && !stdenv.cc.isClang) [
      "-DPYBIND11_CXX_STANDARD=-std=c++17"
  
negative.code: 
  buildPythonPackage rec {
    pname = "pybind11";
    version = "2.8.1";
  
    src = fetchFromGitHub {
      owner = "pybind";
      repo = pname;
      rev = "v${version}";
      sha256 = "sha256-Gk4ZN/g6SRWFm0ALCvyald/9zq3wBd48mGdqdGCeGYI=";
    };
  
    nativeBuildInputs = [ cmake ];
  