anchor.diff:  }:
   
   let
  -  inherit (lib) optionals;
  -
     version = "3.1.1";
   in
   buildPythonPackage rec {
  
positive.code: { stdenv
  , buildPythonPackage
  , fetchPyPi
  , isPy2
  , lib
  , unzip
  
  
negative.code:   propagatedBuildInputs = [
      py-cpuinfo
      pytest
    ];
  
    meta = with lib; {
      description = "py.test fixture for benchmarking code";
  