code: def testDup(self):
      for dtype in datatypes:
          factory = MPI.Datatype.Dup
          self.check(dtype, factory)
  
imports: from mpi4py import MPI
  import mpiunittest
  import struct
label_desc: Use image node_id 4 for calling the BaseTestDatatypeCreateMixin obj's underlying member method code with example usage: obj.testDup() without return types