anchor.diff:  
     pytestFlagsArray = [
       # parallelize
  -    "--numprocesses auto"
  +    "--numprocesses $NIX_BUILD_CORES"
       # rerun failed tests up to three times
       "--reruns 3"
       # don't run tests that require network access
  
positive.code: 
  buildPythonPackage rec {
    pname = "dask";
    version = "2021.10.0";
    format = "setuptools";
  
    disabled = pythonOlder "3.7";
  
negative.code:     owner = "dask";
      repo = pname;
      rev = version;
      sha256 = "sha256-HlVvnhEDzefzv9xchlXl9d4KCumoAqoYUWmIiCXLJyM=
  ";
    };
  
    propagatedBuildInputs = [
      cloudpickle
  