code: def testZero(self):
      inputc = numpy.array([complex()] * 4, dtype="c8")
  
      mag, phase = CartesianToPolar()(inputc)
      self.assertEqualVector(mag, zeros(4))
      self.assertEqualVector(phase, zeros(4))
  
imports: from essentia_test import *
  from math import *
label_desc: Use image node_id 1 for calling the TestCartesianToPolar obj's underlying member method code with example usage: obj.testZero() without return types