code: def testMulti(self):
      input = [5, 8, 4, 9, 1]
      self.assertAlmostEqual(PowerMean()(input), 5.4)
      self.assertAlmostEqual(PowerMean(power=0)(input), 4.28225474)
      self.assertAlmostEqual(PowerMean(power=-3)(input), 1.69488507)
      self.assertAlmostEqual(PowerMean(power=4)(input), 6.93105815)
  
file_path: essentia/test/src/unittests/stats/test_powermean.py
imports: from essentia_test import *
label_desc: Use image node_id 4 for calling the TestPowerMean obj's underlying member method code with example usage: obj.testMulti() without return types