anchor.diff:  
   buildPythonPackage rec {
     pname = "chainer";
  -  version = "6.5.0";
  +  version = "7.7.0";
     disabled = !isPy3k; # python2.7 abandoned upstream
   
     # no tests in Pypi tarball
  
positive.code: 
    # avoid gpu tests
    checkPhase = ''
      pytest tests/chainer_tests/utils_tests -k 'not gpu and not cupy'
    '';
  
    meta = with lib; {
  
negative.code:     owner = "chainer";
      repo = "chainer";
      rev = "v${version}";
      sha256 = "0m97k5bv4pcp5rvbczvrr2vxddwzw2h42cm021f5y779jx5ghclh";
    };
  
    checkInputs = [
      pytest
  