anchor.diff:  
     disabled = pythonOlder "3.7";
   
  -  src = fetchPypi {
  -    inherit pname version;
  -    hash = "sha256-uAcm/B+4mg6Pi+HnfijQAmsejtkLwUPIoMdiLk+M3Z4=";
  +  src = fetchFromGitHub {
  +    owner = "jupyter";
  +    repo = pname;
  +    rev = "refs/tags/v${version}";
  +    hash = "sha256-ofyJNJeNkXbZ9qHLTuzJ13PgEXU9lDQ9NkT4nG/R8Ic=";
     };
   
     propagatedBuildInputs = [ async_generator traitlets nbformat nest-asyncio jupyter-client ];
  
positive.code:   # circular dependencies if enabled by default
    doCheck = false;
  
    checkInputs = [ pytestCheckHook xmltodict nbconvert ipywidgets ];
  
    preCheck = ''
      export HOME=$(mktemp -d)
  
negative.code: { async_generator
  , buildPythonPackage
  , fetchFromGitHub
  , ipykernel
  , ipywidgets
  , jupyter-client
  , lib
  , nbconvert
  , nbformat
  , nest-asyncio
  , pytest-asyncio
  , pytestCheckHook
  , pythonOlder
  , traitlets
  , xmltodict
  }:
  
  let nbclient = buildPythonPackage rec {
  