code: def testLeft(self):
      self.assertEqualVector(
          MonoMixer(type="left")(self.clickTrack(), 2), self.left
      )
  
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 2 for calling the TestMonoMixer_Streaming obj's underlying member method code with example usage: obj.testLeft() without return types