code: def test_conversion(self):
      # Check the conversion functions
      s = TransferFunction([1, 0], [1, -1], dt=0.05)
      assert_(isinstance(s.to_ss(), StateSpace))
      assert_(isinstance(s.to_tf(), TransferFunction))
      assert_(isinstance(s.to_zpk(), ZerosPolesGain))
  
      # Make sure copies work
      assert_(TransferFunction(s) is not s)
      assert_(s.to_tf() is not s)
  
imports: from __future__ import division, print_function, absolute_import
  import numpy
  from numpy.testing import assert_equal, assert_array_almost_equal, assert_array_equal, assert_allclose, assert_, assert_almost_equal
  from pytest import raises
  from scipy._lib._numpy_compat import suppress_warnings
  from scipy.signal import dlsim, dstep, dimpulse, tf2zpk, lti, dlti, StateSpace, TransferFunction, ZerosPolesGain, dfreqresp, dbode, BadCoefficients
label_desc: Use image node_id 2 for calling the TestTransferFunction obj's underlying member method code with example usage: obj.test_conversion() without return types