anchor.diff:  { lib
   , buildPythonPackage
   , fetchPypi
  -, fetchpatch
  -, isPy27
  -, future
  +, pythonOlder
   , h5py
   , ipython
   , numba
  
positive.code:     "veryslow"
      "test_algebra_initialisation"
      "test_cga"
      "test_estimate_rotor_sequential[random_sphere]"
    ];
  
    meta = with lib; {
      description = "Numerical Geometric Algebra Module";
      homepage = "https://clifford.readthedocs.io";
      license = licenses.bsd3;
      maintainers = [ maintainers.costrouc ];
      # many TypeError's in tests
      broken = true;
    };
  }
  
negative.code: 
  buildPythonPackage rec {
    pname = "clifford";
    version = "1.4.0";
  
    disabled = pythonOlder "3.5";
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "sha256-eVE8FrD0YHoRreY9CrNb8v4v4KrG83ZU0oFz+V+p+Q0=";
    };
  
    propagatedBuildInputs = [
      h5py
      numba
      numpy
  