code: def testSequence(self):
      n = 16
      try:
          mem = MPI.Alloc_mem(n, MPI.INFO_NULL)
      except NotImplementedError:
          self.skipTest("mpi-alloc_mem")
      try:
          self.assertIs(type(mem), MPI.buffer)
          self.assertNotEqual(mem.address, 0)
          self.assertEqual(mem.nbytes, n)
          self.assertFalse(mem.readonly)
          self.assertEqual(len(mem), n)
  
          def delitem():
              del mem[n]
  
          def getitem1():
              return mem[n]
  
          def getitem2():
              return mem[::2]
  
          def getitem3():
              return mem[None]
  
          def setitem1():
              mem[n] = 0
  
          def setitem2():
              mem[::2] = 0
  
          def setitem3():
              mem[None] = 0
  
          self.assertRaises(Exception, delitem)
          self.assertRaises(IndexError, getitem1)
          self.assertRaises(IndexError, getitem2)
          self.assertRaises(TypeError, getitem3)
          self.assertRaises(IndexError, setitem1)
          self.assertRaises(IndexError, setitem2)
          self.assertRaises(TypeError, setitem3)
          for i in range(n):
              mem[i] = i
          for i in range(n):
              self.assertEqual(mem[i], i)
          mem[:] = 0
          for i in range(-n, 0):
              mem[i] = abs(i)
          for i in range(-n, 0):
              self.assertEqual(mem[i], abs(i))
          mem[:] = 0
          for i in range(n):
              self.assertEqual(mem[i], 0)
          mem[:] = 255
          for i in range(n):
              self.assertEqual(mem[i], 255)
          mem[: n // 2] = 1
          mem[n // 2 :] = 0
          for i in range(n // 2):
              self.assertEqual(mem[i], 1)
          for i in range(n // 2, n):
              self.assertEqual(mem[i], 0)
          mem[:] = 0
          mem[1:5] = b"abcd"
          mem[10:13] = b"xyz"
          self.assertEqual(mem[0], 0)
          for i, c in enumerate("abcd"):
              self.assertEqual(mem[1 + i], ord(c))
          for i in range(5, 10):
              self.assertEqual(mem[i], 0)
          for i, c in enumerate("xyz"):
              self.assertEqual(mem[10 + i], ord(c))
          for i in range(13, n):
              self.assertEqual(mem[i], 0)
          self.assertEqual(mem[1:5].tobytes(), b"abcd")
          self.assertEqual(mem[10:13].tobytes(), b"xyz")
      finally:
          MPI.Free_mem(mem)
          self.assertEqual(mem.address, 0)
          self.assertEqual(mem.nbytes, 0)
          self.assertFalse(mem.readonly)
  
file_path: mpi4py/test/test_buffer.py
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 13 for calling the TestBuffer obj's underlying member method code with example usage: obj.testSequence() and returns: mem, mem, mem