code: def testGetExtent(self):
      for dtype in datatypes:
          lb, ext = dtype.Get_extent()
          self.assertEqual(dtype.lb, lb)
          self.assertEqual(dtype.ub, lb + ext)
          self.assertEqual(dtype.extent, ext)
  
imports: from mpi4py import MPI
  import mpiunittest
  import struct
label_desc: Use image node_id 2 for calling the TestDatatype obj's underlying member method code with example usage: obj.testGetExtent() without return types