graphaviz的一些参考
this is the best tutorial: https://www.worthe-it.co.za/programming/2017/09/19/quick-introduction-to-graphviz.html#:~:text=Ranks and Subgraphs,placed further to the right.
https://graphviz.readthedocs.io/en/stable/examples.html
https://graphs.grevian.org/example
https://pygraphviz.github.io/documentation/latest/tutorial.html
https://graphviz.org/doc/info/shapes.html
https://graphviz.org/doc/info/attrs.html
https://pygraphviz.github.io/documentation/pygraphviz-1.3.1/tutorial.html