anchor.diff:      numpy
       scipy
       matplotlib
  -    h5py
  +    h5py-mpi
       cython
       autograd
       mpi4py
  
positive.code:   doCheck = true;
    checkPhase = ''
      export PYTHONPATH="$out/lib/${python.libPrefix}/site-packages:$PYTHONPATH"
      python3 << EOF
      import meep as mp
      cell = mp.Vector3(16,8,0)
      geometry = [mp.Block(mp.Vector3(mp.inf,1,mp.inf),
  
negative.code:     blas
      lapack
      fftw
      hdf5-mpi
      harminv
      libctl
      libGDSII
  