http://www.matrix67.com/blog/archives/160
G
https://wenku.baidu.com/view/f43d8fed172ded630a1cb605.html?sxts=1555840319664
https://wenku.baidu.com/view/be4a0bf32cc58bd63186bd5c.html
多重边解决
http://pygraphviz.github.io/documentation/latest/reference/agraph.html
https://stackoverflow.com/questions/34979125/hierarchical-graph-with-parallel-edges
https://stackoverflow.com/questions/35007046/how-to-draw-parallel-edges-in-networkx-graphviz
https://pygraphviz.github.io/documentation/latest/examples.html 文档
http://www.graphviz.org/doc/info/attrs.html 文档
CSDN
https://www.cnblogs.com/rocketfan/archive/2009/09/09/1563628.html
https://blog.csdn.net/rookie_is_me/article/details/86608771
https://blog.csdn.net/bitcarmanlee/article/details/78037251