code: def test_from_zpk(self, xp, scp):
      # 1st order low-pass filter: H(s) = 0.3 / (z - 0.2),
      system_ZPK = scp.signal.dlti([], [0.2], 0.3)
      system_TF = scp.signal.dlti(0.3, [1, -0.2])
      w = [0.1, 1, 10, 100]
      w1, H1 = scp.signal.dfreqresp(system_ZPK, w=w)
      w2, H2 = scp.signal.dfreqresp(system_TF, w=w)
      return w1, H1, w2, H2
  
imports: from math import sqrt, pi
  from pytest import raises
  import cupy
  from cupy import testing
  import cupyx.scipy.signal
label_desc: Use image node_id 7 for calling the Test_dfreqresp obj's underlying member method code with example usage: obj.test_from_zpk(xp, scp) and returns: w1,  H1,  w2,  H2