code: def testPreallocate(self):
      size = self.FILE.Get_size()
      self.assertEqual(size, 0)
      self.FILE.Preallocate(1)
      size = self.FILE.Get_size()
      self.assertEqual(size, 1)
      self.FILE.Preallocate(100)
      size = self.FILE.Get_size()
      self.assertEqual(size, 100)
      self.FILE.Preallocate(10)
      size = self.FILE.Get_size()
      self.assertEqual(size, 100)
      self.FILE.Preallocate(200)
      size = self.FILE.Get_size()
      self.assertEqual(size, 200)
  
imports: from mpi4py import MPI
  import mpiunittest
  import os, tempfile, pathlib
label_desc: Use image node_id 3 for calling the BaseTestFile obj's underlying member method code with example usage: obj.testPreallocate() without return types