code: def test_gbt(self, xp, scp):
      ac = xp.eye(2)
      bc = xp.full((2, 1), 0.5)
      cc = xp.array([[0.75, 1.0], [1.0, 1.0], [1.0, 0.25]])
      dc = xp.array([[0.0], [0.0], [-0.33]])
  
      dt_requested = 0.5
      alpha = 1.0 / 3.0
  
      c2d = scp.signal.cont2discrete
      ad, bd, cd, dd, dt = c2d(
          (ac, bc, cc, dc), dt_requested, method="gbt", alpha=alpha
      )
      return ad, bd, cd, dd, dt
  
imports: import math
  import cupyx.scipy.signal
  import pytest
  from cupy import testing
label_desc: Use image node_id 4 for calling the TestC2D obj's underlying member method code with example usage: obj.test_gbt(xp, scp) and returns: ad,  bd,  cd,  dd,  dt