using one node to represent a group of nodes in graph.
example
https://colab.research.google.com/drive/1Ksca_p4XrZjeN0A6jT5aYN6ARvwFVSbY?usp=sharing
using one node to represent a group of nodes in graph.
https://colab.research.google.com/drive/1Ksca_p4XrZjeN0A6jT5aYN6ARvwFVSbY?usp=sharing