code: def testNoneObserver(self):
      sample = read_sample(SIMPLE_SAMPLES.SAMPLE_SIMPLE1)
      ga_instance = genetic_algorithm(
          sample,
          2,
          20,
          20,
          count_mutation_gens=2,
          coeff_mutation_count=0.25,
          observer=None,
      )
      ga_instance.process()
  
      self.assertIsNone(ga_instance.get_observer())
  
imports: import unittest
  import inspect
  import numpy
  import matplotlib
  from pyclustering.samples.definitions import SIMPLE_SAMPLES
  from pyclustering.cluster.ga import genetic_algorithm, ga_observer, ga_visualizer
  from pyclustering.cluster.ga_maths import ga_math
  from pyclustering.utils import read_sample
label_desc: Use image node_id 28 for calling the GeneticAlgorithmClusteringUnitTest obj's underlying member method code with example usage: obj.testNoneObserver() without return types