anchor.diff:  { stdenv
   , buildPythonPackage
   , fetchPyPi
  +, isPy2
   , lib
   , unzip
   
  +, py-cpuinfo
   , pytest
   , statistics
   }:
   
   let
  -  version = "3.0.0";
  +  inherit (lib) optionals;
  +
  +  version = "3.1.1";
   in
   buildPythonPackage rec {
     name = "pytest-benchmark-${version}";
  
positive.code:   ];
  
    propagatedBuildInputs = [
      pytest
      statistics
    ];
  
    doCheck = true;
  
    meta = with lib; {
      description = "py.test fixture for benchmarking code";
  
negative.code:   src = fetchPyPi {
      package = "pytest-benchmark";
      inherit version;
      sha256 = "185526b10b7cf1804cb0f32ac0653561ef2f233c6e50a9b3d8066a9757e36480";
    };
  
    nativeBuildInputs = [
  