anchor.diff:      freezegun
     ];
   
  -  pytestFlagsArray = lib.optionals (!withContribRequires) [
  +  disabledTestPaths = lib.optionals (!withContribRequires) [
       # requires external (unpackaged) libraries, so untested.
  -    "--ignore=cirq/contrib/"
  +    "cirq/contrib/"
     ];
     disabledTests = [
       "test_metadata_search_path" # tries to import flynt, which isn't in Nixpkgs
  
positive.code: 
  buildPythonPackage rec {
    pname = "cirq-core";
    version = "0.13.1";
  
    disabled = pythonOlder "3.6";
  
  
negative.code:     owner = "quantumlib";
      repo = "cirq";
      rev = "v${version}";
      sha256 = "sha256-cIDwV3IBXrTJ4jC1/HYmduY3tLe/f6wj8CWZ4cnThG8=";
    };
  
    sourceRoot = "source/${pname}";
  
    postPatch = ''
      substituteInPlace requirements.txt \
        --replace "matplotlib~=3.0" "matplotlib" \
        --replace "networkx~=2.4" "networkx" \
        --replace "numpy~=1.16" "numpy" \
        --replace "sympy<1.10" "sympy"
    '';
  
    propagatedBuildInputs = [
  