code: def testRegression(self):
      expected = 0.021876449  # from scipy Welch [https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.signal.welch.html]
  
      audio = MonoLoader(
          filename=join(testdata.audio_dir, "recorded/vignesh.wav")
      )()
      esWelch = Welch(
          fftSize=256, frameSize=256, scaling="density", sampleRate=1.0
      )
  
      psdList = []
      for frame in FrameGenerator(audio, frameSize=256, hopSize=256):
          psdList.append(esWelch(frame))
      result = numpy.mean(numpy.array(psdList))
  
      self.assertAlmostEqual(result, expected, 1e-1)
  
imports: from essentia_test import *
label_desc: Use image node_id 1 for calling the TestWelch obj's underlying member method code with example usage: obj.testRegression() without return types