anchor.diff:  { lib
   , buildPythonPackage
   , fetchPypi
  +, pythonAtLeast
   , six
   , pygraphviz
   , pytestCheckHook
  
positive.code:     export HOME=$TMPDIR
    '';
  
    meta = with lib; {
      homepage = "https://github.com/pytransitions/transitions";
      description = "A lightweight, object-oriented finite state machine implementation in Python";
  
negative.code: buildPythonPackage rec {
    pname = "transitions";
    version = "0.8.10";
    format = "setuptools";
  
    src = fetchPypi {
      inherit pname version;
  