code: def test_clustering_directed_small(self):
      g = Graph.Ring(5, directed=True)
      clu = VertexClustering(g, [0] * 5)
      lo = g.layout("auto")
      plot(
          clu,
          layout=lo,
          backend="cairo",
          target=result_image_folder / "clustering_directed.png",
          mark_groups=True,
      )
  
imports: import random
  import unittest
  from igraph import Graph, plot, VertexClustering
label_desc: Use image node_id 3 for calling the ClusteringTestRunner obj's underlying member method code with example usage: obj.test_clustering_directed_small() without return types