code: def testObserver(self):
      sample = read_sample(SIMPLE_SAMPLES.SAMPLE_SIMPLE2)
  
      means, variances = ema_initializer(sample, 3).initialize(
          ema_init_type.RANDOM_INITIALIZATION
      )
  
      observer_instance = ema_observer()
      ema_instance = ema(sample, 3, means, variances, observer_instance)
      ema_instance.process()
  
      observer_length = len(observer_instance)
      assert observer_length > 0
      assert observer_length == len(
          observer_instance.get_evolution_clusters()
      )
      assert observer_length == len(
          observer_instance.get_evolution_covariances()
      )
      assert observer_length == len(
          observer_instance.get_evolution_means()
      )
      assert observer_length == observer_instance.get_iterations()
  
imports: import unittest
  import matplotlib
  from pyclustering.cluster.ema import ema, ema_observer, ema_initializer, ema_init_type, ema_visualizer
  from pyclustering.utils import read_sample
  from pyclustering.samples.definitions import SIMPLE_SAMPLES, FCPS_SAMPLES, FAMOUS_SAMPLES
label_desc: Use image node_id 29 for calling the EmaUnitTest obj's underlying member method code with example usage: obj.testObserver() without return types