Hi Tiago,
I am on Ubuntu 16.04 and today I updated from git: '2.23 (commit b669e1b7, Sun Sep 24 00:01:08 2017 +0200)'.
Till now, I was at least able to draw two graphs in two subplots as said in my previous email. However, today even that is not working. My code:
import graph_tool.all as gt
import matplotlib.pyplot as plt
plt.switch_backend('cairo')
g1 = gt.collection.data['karate']
g2 = gt.collection.data['dolphins']
ax = plt.subplot(1, 2, 1)
gt.graph_draw(g1, mplfig = ax)
ax = plt.subplot(1, 2, 2)
gt.graph_draw(g2, mplfig = ax)
ax = plt.subplot(2, 2, 3)
plt.savefig('test.pdf')