anchor.diff:  , scipy
   , scikit-learn
   , persim
  -, pytest
  +, pytestCheckHook
   }:
   
   buildPythonPackage rec {
  
positive.code: { lib
  , buildPythonPackage
  , fetchPypi
  , pythonOlder
  , cython
  
negative.code:     persim
    ];
  
    checkInputs = [
      pytestCheckHook
    ];
  
    preCheck = ''
      # specifically needed for darwin
      export HOME=$(mktemp -d)
      mkdir -p $HOME/.matplotlib
      echo "backend: ps" > $HOME/.matplotlib/matplotlibrc
    '';
  
    meta = with lib; {
  