anchor.diff: -{ stdenv, buildPythonPackage, fetchFromGitHub
  +{ lib, buildPythonPackage, fetchFromGitHub
   , cython
   , libxml2
   , libxslt
  
positive.code: 
    pythonImportsCheck = [ "lxml" "lxml.etree" ];
  
    meta = with stdenv.lib; {
      description = "Pythonic binding for the libxml2 and libxslt libraries";
      homepage = "https://lxml.de";
      license = licenses.bsd3;
  
negative.code: 
  buildPythonPackage rec {
    pname = "lxml";
    version = "4.5.2";
  
    src = fetchFromGitHub {
      owner = pname;
      repo = pname;
      rev = "${pname}-${version}";
      sha256 = "1d0cpwdjxfzwjzmnz066ibzicyj2vhx15qxmm775l8hxqi65xps4";
    };
  
    # setuptoolsBuildPhase needs dependencies to be passed through nativeBuildInputs
  