code: def testDirected(self):
      g = Graph(
          6,
          [
              (0, 1),
              (0, 2),
              (1, 2),
              (1, 3),
              (1, 4),
              (2, 4),
              (3, 4),
              (3, 5),
              (4, 5),
          ],
          directed=True,
      )
      g.es["capacity"] = [1, 7, 1, 3, 2, 4, 1, 6, 2]
      self.assertRaises(InternalError, g.gomory_hu_tree, "capacity")
  
imports: import unittest
  from igraph import Cut, Graph, EdgeSeq, InternalError
  from itertools import combinations
  from random import randint
label_desc: Use image node_id 3 for calling the GomoryHuTests obj's underlying member method code with example usage: obj.testDirected() without return types