code: def testDecomposeUndirected(self):
      g = Graph([(0, 1), (1, 2), (2, 3)], n=4, directed=False)
      components = g.decompose()
  
      assert len(components) == 1
      assert components[0].isomorphic(g)
  
      g = Graph.Full(5) + Graph.Full(3)
      components = g.decompose()
  
      assert len(components) == 2
      assert components[0].isomorphic(Graph.Full(5))
      assert components[1].isomorphic(Graph.Full(3))
  
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 1 for calling the DecompositionTests obj's underlying member method code with example usage: obj.testDecomposeUndirected() without return types