code: def test_transferfunction(self):
      numc = np.array([0.25, 0.25, 0.5])
      denc = np.array([0.75, 0.75, 1.0])
  
      numd = np.array(
          [[1.0 / 3.0, -0.427419169438754, 0.221654141101125]]
      )
      dend = np.array([1.0, -1.351394049721225, 0.606530659712634])
  
      dt_requested = 0.5
  
      num, den, dt = c2d((numc, denc), dt_requested, method="zoh")
  
      assert_array_almost_equal(numd, num)
      assert_array_almost_equal(dend, den)
      assert_almost_equal(dt_requested, dt)
  
imports: from __future__ import division, print_function, absolute_import
  import numpy
  from numpy.testing import assert_array_almost_equal, assert_almost_equal, assert_allclose, assert_equal
  import warnings
  from scipy.signal import cont2discrete
  from scipy.signal import dlsim, ss2tf, ss2zpk, lsim2, lti
label_desc: Use image node_id 6 for calling the TestC2D obj's underlying member method code with example usage: obj.test_transferfunction() without return types