anchor.diff:    patsy = buildPythonPackage rec {
       name = "patsy-${version}";
       version = "0.3.0";
  -    
  +
       src = pkgs.fetchurl{
         url = "https://pypi.python.org/packages/source/p/patsy/${name}.zip";
         md5 = "7545518b413136ba8343dcebea07e5e2";
       };
  -    
  +
       propagatedBuildInputs = with self; [six numpy];
  -    
  +
       meta = {
         description = "A Python package for describing statistical models";
         homepage = "https://github.com/pydata/patsy";
         license = licenses.bsd2;
       };
     };
  -  
  +
     paste = buildPythonPackage rec {
       name = "paste-1.7.5.1";
       disabled = isPy3k;
  
positive.code:   toolz = buildPythonPackage rec{
      name = "toolz-${version}";
      version = "0.7.2";
      
      src = pkgs.fetchurl{
        url = "https://pypi.python.org/packages/source/t/toolz/toolz-${version}.tar.gz";
        md5 = "6f045541a9e7ee755b7b00fced4a7fde";
      };
      
      meta = {
        homepage = "http://github.com/pytoolz/toolz/";
        description = "List processing tools and functional utilities";
        license = "licenses.bsd3";   
      };
    };
    
    tox = buildPythonPackage rec {
      name = "tox-1.8.1";
  
  
negative.code:   multipledispatch = buildPythonPackage rec {
      name = "multipledispatch-${version}";
      version = "0.4.8";
  
      src = pkgs.fetchurl {
        url = "https://pypi.python.org/packages/source/m/multipledispatch/${name}.tar.gz";
        sha256 = "07d41fb3ed25e8424536e48a8566f88a0f9926ca4b6174bff6aa16c98251b92e";
      };
  
      meta = {
        homepage = http://github.com/mrocklin/multipledispatch/;
        description = "A relatively sane approach to multiple dispatch in Python";
  