anchor.diff: -{ lib
  +{ stdenv
   , buildPythonPackage
   , fetchPypi
   , cmake
   , numpy
   , scipy
   , scikitlearn
  +, llvmPackages ? null
   }:
   
   buildPythonPackage rec {
  
positive.code:     cmake
    ];
  
    propagatedBuildInputs = [
      numpy
      scipy
  
negative.code: 
    postConfigure = ''
      export HOME=$(mktemp -d)
    '' + stdenv.lib.optionalString stdenv.cc.isClang ''
      export NIX_LDFLAGS="$NIX_LDFLAGS -L${llvmPackages.openmp}/lib -lomp"
    '';
  
    # The pypi package doesn't distribute the tests from the GitHub
  