Add the function path into the shell resource file (e.g., .bash_profile or .bashrc) under your home folder.
export PYTHONPATH=$PYTHONPATH:</path/to/your/cloned/pylibs/repo>
For instance, I cloned this repo to /home/swei/research/pyscripts/pylibs, then in the .bash_profile.
export PYTHONPATH=$PYTHONPATH:/home/swei/research/pyscripts/pylibs