code: def testMix(self):
      mix = MonoMixer(type="mix")(self.clickTrack(), 2)
      self.assertEqual(sum(mix), 19 * 0.5)
  
file_path: essentia/test/src/unittests/standard/test_monomixer.py
imports: from essentia_test import *
  from essentia import *
  from numpy import sum
label_desc: Use image node_id 4 for calling the TestMonoMixer_Streaming obj's underlying member method code with example usage: obj.testMix() without return types