code: def test_conversion(self):
      # Check the conversion functions
      s = signal.StateSpace(1, 2, 3, 4, dt=0.05)
      assert isinstance(s.to_ss(), signal.StateSpace)
      assert isinstance(s.to_tf(), signal.TransferFunction)
      assert isinstance(s.to_zpk(), signal.ZerosPolesGain)
  
      # Make sure copies work
      assert signal.StateSpace(s) is not s
      assert s.to_ss() is not s
  
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 2 for calling the TestStateSpaceDisc obj's underlying member method code with example usage: obj.test_conversion() without return types