code: def _map_device_string(self, device):
      return "cuda" if device == "gpu" else "cpu"
  
imports: import copy
  import math
  import unittest
  import unittest.mock
  import torch
  import torch.nn
  from classy_vision.hooks import ExponentialMovingAverageModelHook
  from classy_vision.models import ClassyModel
  from test.generic.hook_test_utils import HookTestBase
label_desc: Use image node_id 1 for calling the TestExponentialMovingAverageModelHook obj's underlying member method code with example usage: obj._map_device_string(device) and returns: unknown