code: def testHostPorcessor(self):
      size = MPI.COMM_WORLD.Get_size()
      vals = list(range(size)) + [MPI.PROC_NULL]
      hostproc = MPI.COMM_WORLD.Get_attr(MPI.HOST)
      if hostproc is not None:
          self.assertIn(hostproc, vals)
  
imports: from mpi4py import MPI
  import mpiunittest
  import os
label_desc: Use image node_id 2 for calling the TestWorldAttrs obj's underlying member method code with example usage: obj.testHostPorcessor() without return types