code: def testSubarray(self):
      for dtype in datatypes:
          for ndim in range(1, 5):
              for size in range(1, 5):
                  for subsize in range(1, size):
                      for start in range(size - subsize):
                          for order in [
                              MPI.ORDER_C,
                              MPI.ORDER_FORTRAN,
                              MPI.ORDER_F,
                          ]:
                              sizes = [size] * ndim
                              subsizes = [subsize] * ndim
                              starts = [start] * ndim
                              factory = MPI.Datatype.Create_subarray
                              args = sizes, subsizes, starts, order
                              self.check(dtype, factory, *args)
  
imports: from mpi4py import MPI
  import mpiunittest
  import struct
label_desc: Use image node_id 13 for calling the BaseTestDatatypeCreateMixin obj's underlying member method code with example usage: obj.testSubarray() without return types