anchor.diff:  
   RUN pip install --user --no-cache-dir -r $HOME/riemann_book/requirements.txt
   
  -CMD jupyter notebook riemann_book/Index.ipynb --ip='*' --no-browser
  +# The command below starts the notebook server, but better to not
  +# do this by default in case the user also wants to examine files or use
  +# the docker container for running other things...
  +#CMD jupyter notebook riemann_book/Index.ipynb --ip=0.0.0.0 --port=8889 --no-browser
  +
  
positive.code: WORKDIR ${HOME}
  
  
  # Install notebook extensions
  #RUN pip install --user --no-cache-dir \
      #jupyter \
      #jupyter_contrib_nbextensions \
      #jupyterhub-legacy-py2-singleuser==0.7.2
  
  RUN git clone https://github.com/ipython-contrib/jupyter_contrib_nbextensions.git
  RUN pip install --user -e jupyter_contrib_nbextensions
  
  ENV PATH ${PATH}:/home/jovyan/.local/bin
  
negative.code: 
  FROM clawpack/v5.6.1_dockerimage:release
  # this dockerhub image has a user jovyan and clawpack installed 
  # in /home/jovyan/clawpack-v5.6.1
  
  
  ENV NB_USER jovyan
  