Problem in your colab demo
There are problems in installing graph-tool
By running your own Google colab notebook (https://colab.research.google.com/github/count0/colab-gt/blob/master/colab-gt.ipynb), we get this error:
ModuleNotFoundError Traceback (most recent call last) in ----> 1 from graph_tool.all import * 2 3 g = collection.data["celegansneural"] 4 state = minimize_nested_blockmodel_dl(g)
ModuleNotFoundError: No module named 'graph_tool'