code: def test_incorrect_kstep(self):
      self.assertRaises(
          ValueError, elbow, [[0], [1], [2]], 1, 3, kstep=0
      )
  
imports: import unittest
  import matplotlib
  from pyclustering.cluster.center_initializer import random_center_initializer
  from pyclustering.cluster.elbow import elbow
  from pyclustering.cluster.tests.elbow_template import elbow_test_template
  from pyclustering.samples.definitions import SIMPLE_SAMPLES, SIMPLE_ANSWERS
label_desc: Use image node_id 32 for calling the elbow_unit_test obj's underlying member method code with example usage: obj.test_incorrect_kstep() without return types