Graphviz must be installed on host system. (see https://graphviz.org/download/)
Don't forget to include dot executable in your PATH. (File is often there: /usr/local/bin/dot)

huffman-py installation:

preferred method:

cd <path to cloned git>
pip install .

alternative method:

cd <path to cloned git>
python setup.py build
python setup.py install

Will create a huffman_py file to run the application. (Should be in ~/.local/bin)

checks:

to run unit tests:

cd <path to cloned git>
python -m unittest discover