code: def testValueIndex(self):
      integral_types = datatypes_c[2:-3] + datatypes_c99[1:9]
      floating_types = datatypes_c[-3:]
      value_types = integral_types + floating_types
      index_types = integral_types
      for value in value_types:
          if value == MPI.DATATYPE_NULL:
              continue
          for index in index_types:
              if index == MPI.DATATYPE_NULL:
                  continue
              factory = MPI.Datatype.Get_value_index
              pair = factory(value, index)
              if pair == MPI.DATATYPE_NULL:
                  continue
              if pair.is_named:
                  continue
              self.check(None, factory, value, index)
  
imports: from mpi4py import MPI
  import mpiunittest
  import struct
label_desc: Use image node_id 21 for calling the BaseTestDatatypeCreateMixin obj's underlying member method code with example usage: obj.testValueIndex() without return types