anchor.diff: -FROM ubuntu:18.04
  +FROM ubuntu:18.04 as base
   RUN apt update
   RUN dpkg --add-architecture i386 && apt update
   RUN apt-get -y install \
  
positive.code:     python3-setuptools \
      python3-wheel \
      sudo
  
  RUN sudo pip3 install --upgrade pip
  RUN sudo pip3 install matplotlib
  
negative.code: # install
  COPY . .
  RUN ./install.sh
  RUN pip3 install --upgrade setuptools testresources 
  RUN pip3 install --upgrade -r requirements.txt
  RUN pip3 install --upgrade cmake
  
  # build and test
  RUN mkdir -p build
  WORKDIR /repo/build
  RUN cmake -DPython_TARGET_VERSION=${PYVERSION} -DCMAKE_CXX_COMPILER=`which clang++` ../open_spiel 
  RUN make -j12
  RUN ctest -j12
  ENV PYTHONPATH=${PYTHONPATH}:/repo
  ENV PYTHONPATH=${PYTHONPATH}:/repo/build/python
  WORKDIR /repo/open_spiel
  
  # minimal image for development in Python
  FROM python:3.6-slim-buster as python-slim
  RUN mkdir repo
  WORKDIR /repo
  COPY --from=base /repo .
  RUN pip3 install --upgrade -r requirements.txt
  RUN pip3 install matplotlib
  ENV PYTHONPATH=${PYTHONPATH}:/repo
  ENV PYTHONPATH=${PYTHONPATH}:/repo/build/python
  WORKDIR /repo/open_spiel
  