code: def delta(self) -> int:
      return self.active_memory_exit - self.active_memory_enter
  
imports: import unittest
  from collections import deque, OrderedDict
  from contextlib import ContextDecorator
  from copy import deepcopy
  from typing import Tuple
  import torch
  import torch.nn
  from torch.distributed._composable import checkpoint
  from torch.testing._internal.common_cuda import TEST_CUDA
  from torch.testing._internal.common_utils import run_tests, TestCase
label_desc: Use image node_id 4 for calling the MemoryDelta obj's underlying member method code with example usage: obj.delta() and returns: unknown