code: def test_mark_groups(self):
      g = Graph.Ring(5, directed=True)
      fig = go.Figure()
      plot(
          g, target=fig, mark_groups=True, layout=self.layout_small_ring
      )
      return fig
  
imports: import unittest
  from igraph import Graph, plot, VertexClustering
label_desc: Use image node_id 5 for calling the GraphTestRunner obj's underlying member method code with example usage: obj.test_mark_groups() and returns: fig