code: def test_hstack_vectors(self, xp):
      a = xp.arange(3)
      b = xp.arange(2, -1, -1)
      return xp.hstack((a, b))
  
imports: import numpy
  import pytest
  import cupy
  from cupy import testing
  from cupy import cuda
label_desc: Use image node_id 33 for calling the TestJoin obj's underlying member method code with example usage: obj.test_hstack_vectors(xp) and returns: xp