anchor.diff:  # Prepare files and permissions
   #
   
  -# Copy notebooks into place
  -COPY . $HOME
  -
   # As root, adjust permissions on notebooks
   USER root
   RUN chown -Rv $NB_USER:users $HOME/*.ipynb
  
positive.code: RUN pip3 install --no-cache-dir pandeia.engine==$PANDEIA_VERSION
  
  # Extract Pandeia reference data into $HOME/pandeia_wfirst_data
  ADD pandeia_wfirst_data.tar.gz
  RUN tar xvz pandeia_wfirst_data.tar.gz
  ENV pandeia_refdata $HOME/pandeia_wfirst_data
  
  
negative.code: 
  WORKDIR $HOME
  USER $NB_USER
  
  # Copy notebooks into place
  COPY . $HOME
  
  # Note: this Dockerfile is ordered roughly by how often things are expected
  # to change (ascending). That way, only the last few changed steps are
  