anchor.diff:  { lib
  +, attrs
   , buildPythonPackage
  +, docutils
   , fetchPypi
  -
  -# build
  +, od
  +, pygments
  +, pytestCheckHook
  +, python-dateutil
   , setuptools
  -
  -# propagtes
   , sigtools
  -, six
  -, attrs
  -, od
  -, docutils
  -
  -# extras: datetime
  -, python-dateutil
  -
  -# tests
  -, pygments
   , unittest2
  -, pytestCheckHook
   }:
   
   buildPythonPackage rec {
  
positive.code:   version = "5.0.0";
    format = "pyproject";
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "sha256-/cFpEvAN/Movd38xaE53Y+D9EYg/SFyHeqtlVUo1D0I=";
    };
  
    postPatch = ''
      substituteInPlace setup.py \
        --replace "docutils ~= 0.17.0" "docutils" \
        --replace "attrs>=19.1.0,<22" "attrs>=19.1.0"
    '';
  
    nativeBuildInputs = [
      setuptools
  
negative.code:     docutils
      od
      sigtools
    ];
  
    passthru.optional-dependencies = {
  