anchor.diff:  
     prePatch = ''
       substituteInPlace setup.py \
  -      --replace "pathlib==1.0.1" "pathlib>=1.0.0,<2.0.0" \
  -      --replace "plac>=0.9.6,<1.0.0" "plac>=0.9.6" \
  -      --replace "msgpack-numpy<0.4.4" "msgpack-numpy" \
  -      --replace "wheel>=0.32.0,<0.33.0" "wheel" \
  -      --replace "wrapt>=1.10.0,<1.11.0" "wrapt" \
  -      --replace "msgpack>=0.5.6,<0.6.0" "msgpack"
  +      --replace "plac>=0.9.6,<1.0.0" "plac>=0.9.6"
     '';
   
     # Cannot find cython modules.
  
positive.code: , mock
  , wrapt
  , dill
  }:
  
  buildPythonPackage rec {
    pname = "thinc";
    version = "6.12.1";
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "1kkp8b3xcs3yn3ia5sxrh086c9xv27s2khdxd17abdypxxa99ich";
    };
  
    buildInputs = lib.optionals stdenv.isDarwin (with darwin.apple_sdk.frameworks; [
  
negative.code:    cytoolz
     plac
     six
     srsly
     wrapt
     dill
     wasabi
    ] ++ lib.optional (pythonOlder "3.4") pathlib;
  
  
  