docstr: Test method='gbt' with alpha=0.25 for tf and zpk cases.
docstr_tok: ["Test","method='gbt","'","with","alpha=0.25","for","tf","and","zpk","cases","."]
code: def test_gbt_with_sio_tf_and_zpk(self, xp, scp):
      """Test method='gbt' with alpha=0.25 for tf and zpk cases."""
      # State space coefficients for the continuous SIO system.
      A = -1.0
      B = 1.0
      C = 1.0
      D = 0.5
  
      # The continuous transfer function coefficients.
      cnum, cden = scp.signal.ss2tf(A, B, C, D)
  
      # Continuous zpk representation
      cz, cp, ck = scp.signal.ss2zpk(A, B, C, D)
  
      h = 1.0
      alpha = 0.25
  
      # Compute the discrete tf using cont2discrete.
      c2d = scp.signal.cont2discrete
      c2dnum, c2dden, dt = c2d(
          (cnum, cden), h, method="gbt", alpha=alpha
      )
      return c2dnum, c2dden, dt
  
imports: import math
  import cupyx.scipy.signal
  import pytest
  from cupy import testing
label_desc: Use image node_id 10 for calling the TestC2D obj's underlying member method code with example usage: obj.test_gbt_with_sio_tf_and_zpk(xp, scp) and returns: c2dnum,  c2dden,  dt