anchor.diff:  # Default command: force grid demo.
   CMD ["/usr/bin/python3", "demo_forcegrid.py", \
        "--noviewer", \
  -     "--numcubes", "4,4,1"]
  +     "--cubes", "4,4,1"]
  
positive.code: RUN mkdir -p /demo/mongodb
  
  # Add APT credentials for MongoDB.
  RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10
  RUN echo 'deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart' \
           ' dist 10gen' | tee /etc/apt/sources.list.d/10gen.list
  
  # Install Ubuntu packages for Azrael.
  RUN apt-get update && apt-get install -y \
  
negative.code:     libassimp-dev \
      libassimp3 \
      libboost-python-dev \
      mongodb-org \
      python3-matplotlib \
      python3-netifaces \
      python3-numpy \
  