code: def testRegression(self):
      sr = 44100.0
      pi2 = 2 * pi
      signal = [
          0.25 * cos(t * pi2 * 5 / sr)
          + 0.25 * cos(t * pi2 * 50 / sr)
          + 0.25 * cos(t * pi2 * 500.0 / sr)
          + 0.25 * cos(t * pi2 * 5000.0 / sr)
          for t in range(44100)
      ]
  
      filteredSignal = LowPass(cutoffFrequency=1000)(signal)
  
      s = Spectrum()(signal)
      sf = Spectrum()(filteredSignal)
  
      for i in range(1000):
          if s[i] > 10:
              self.assertTrue(sf[i] > 0.5 * s[i])
  
      for i in range(1001, len(sf)):
          if s[i] > 10:
              self.assertTrue(sf[i] < 0.5 * s[i])
  
imports: from essentia_test import *
  from math import *
label_desc: Use image node_id 1 for calling the TestLowPass obj's underlying member method code with example usage: obj.testRegression() without return types