code: def testDecomposeDirected(self):
      g = Graph([(0, 1), (1, 2), (2, 3)], n=4, directed=True)
      components = g.decompose()
  
      g1 = Graph(1, directed=True)
      assert len(components) == 4
      for component in components:
          assert component.isomorphic(g1)
  
imports: import math
  import random
  import unittest
  from igraph import Clustering, CohesiveBlocks, Cover, Graph, Histogram, InternalError, UniqueIdGenerator, VertexClustering, compare_communities, split_join_distance, set_random_number_generator
label_desc: Use image node_id 2 for calling the DecompositionTests obj's underlying member method code with example usage: obj.testDecomposeDirected() without return types