code: def test_invres(self, xp, scp, rpk):
      r, p, k = map(xp.asarray, rpk)
      b, a = scp.signal.invres(r, p, k)
      return b, a
  
imports: import numpy
  import pytest
  import cupy
  from cupy import testing
  import cupyx.scipy.signal
label_desc: Use image node_id 14 for calling the TestPartialFractionExpansion obj's underlying member method code with example usage: obj.test_invres(xp, scp, rpk) and returns: b,  a