anchor.diff:  
   ## pyenv setup
   RUN git clone --quiet --depth 1 https://github.com/yyuu/pyenv.git ${HOME}/.pyenv && \
  -    echo 'PYENV_ROOT ${HOME}/.pyenv' >> ${HOME}/.bashrc && \
  +    echo 'export PYENV_ROOT=${HOME}/.pyenv' >> ${HOME}/.bashrc && \
       echo 'eval "$(pyenv init -)"' >> ${HOME}/.bashrc
  -ENV PATH ${HOME}/.pyenv/shims:${HOME}/.pyenv/bin:${PATH}
   
   ## pyenv-virtualenv plugin
   RUN git clone https://github.com/yyuu/pyenv-virtualenv.git ${HOME}/.pyenv/plugins/pyenv-virtualenv
  
positive.code: ## working environment for developer
  RUN mkdir -p ${HOME}/workspace && \
      byobu-enable
  
  ## docker configurations
  VOLUME ["${HOME}/workspace"]
  
negative.code: RUN env DEBIAN_FRONTEND=noninteractive apt-get update && \
      apt-get -q -y upgrade && \
      apt-get -q -y install \
        make build-essential llvm curl git sudo byobu \
        libc6-dev libreadline6-dev zlib1g-dev libbz2-dev libncursesw5-dev \
        libssl-dev libgdbm-dev libdb-dev libsqlite3-dev liblzma-dev tk-dev \
        libexpat1-dev libmpdec-dev libffi-dev libzmq3-dev pandoc mime-support locales-all && \
      apt-get clean
  
  ## user setup
  RUN useradd -G sudo -m pyuser && \
      echo "Defaults    !authenticate" >> /etc/sudoers
  USER pyuser
  ENV HOME /home/pyuser
  ENV USER pyuser
  