code: def test_incorrect_clusters(self):
      self.assertRaises(
          ValueError, silhouette, [[1], [2], [3], [4]], []
      )
  
imports: import unittest
  import matplotlib
  from pyclustering.cluster.silhouette import silhouette, silhouette_ksearch_type
  from pyclustering.cluster.tests.silhouette_templates import silhouette_test_template
  from pyclustering.samples.definitions import SIMPLE_SAMPLES, SIMPLE_ANSWERS
label_desc: Use image node_id 52 for calling the silhouette_unit_tests obj's underlying member method code with example usage: obj.test_incorrect_clusters() without return types