code: def mpi(f):
      check_available()
      import pytest
  
      try:
          import mpi4py.MPI  # NOQA
  
          available = True
      except ImportError:
          available = False
  
      return unittest.skipUnless(available, "mpi4py is not installed")(
          pytest.mark.mpi(f)
      )
  
imports: import unittest
  from chainer.testing.attr import check_available
  from chainer.testing.attr import gpu
  from chainer.testing.attr import slow
label_desc: Use image node_id 1 for calling a global function with example usage: mpi(f) and returns: unittest