anchor.diff:  { stdenv
   , fetchurl
   , buildPythonPackage
  -, isPy35, isPy27
  +, isPy36, isPy35, isPy27
   , cudaSupport ? false
   , cudatoolkit ? null
   , cudnn ? null
  
positive.code:   version = "1.1.0";
    name = "${pname}-${version}";
    format = "wheel";
    disabled = ! (isPy35 || isPy27);
  
    src = let
        tfurl = sys: proc: pykind:
  
negative.code:             url = tfurl "linux" "cpu" "cp27-none-linux_x86_64";
              sha256 = "0ld3hqx3idxk0zcrvn3p9yqnmx09zsj3mw66jlfw6fkv5hznx8j2";
            };
            py35 = {
              url = tfurl "linux" "cpu" "cp35-cp35m-linux_x86_64";
              sha256 = "0ahz9222rzqrk43lb9w4m351klkm6mlnnvw8xfqip28vbmymw90b";
            };
            py36 = {
              url = tfurl "linux" "cpu" "cp36-cp36m-linux_x86_64";
              sha256 = "1a2cc8ihl94iqff76nxg6bq85vfb7sj5cvvi9sxy2f43k32fi4lv";
            };
  
          };
          linux-x86_64.cuda = {
            py2 = {
              url = tfurl "linux" "gpu" "cp27-none-linux_x86_64";
              sha256 = "1baa9jwr6f8f62dyx6isbw8yyrd0pi1dz1srjblfqsyk1x3pnfvh";
            };
            py35 = {
              url = tfurl "linux" "gpu" "cp35-cp35m-linux_x86_64";
              sha256 = "0606m2awy0ifhniy8lsyhd0xc388dgrwksn87989xlgy90wpxi92";
            };
            py36 = {
              url = tfurl "linux" "gpu" "cp36-cp36m-linux_x86_64";
              sha256 = "0lvbmfa87qzrajadpsf13gi3l71vryzkryzqfvkykivqrdjsvj8q";
            };
  
          };
        };
      in
      fetchurl (
        if stdenv.isDarwin then
          if isPy27 then
            dls.darwin.cpu.py2
          else
            dls.darwin.cpu.py3
        else if isPy36 then
          if cudaSupport then
            dls.linux-x86_64.cuda.py36
          else dls.linux-x86_64.cpu.py36
        else if isPy35 then
          if cudaSupport then
            dls.linux-x86_64.cuda.py35
          else dls.linux-x86_64.cpu.py35
        else
          if cudaSupport then
            dls.linux-x86_64.cuda.py2
  