refactor test (#20300)

- simplifies the devce checking test

tests/mixed_int8/test_mixed_int8.py

@@ -215,23 +215,8 @@ class MixedInt8TestMultiGpu(BaseMixedInt8Test):
             self.model_name, load_in_8bit=True, max_memory=memory_mapping, device_map="auto"
         )
 
-        def get_list_devices(model):
-            list_devices = []
-            for _, module in model.named_children():
-                if len(list(module.children())) > 0:
-                    list_devices.extend(get_list_devices(module))
-                else:
-                    # Do a try except since we can encounter Dropout modules that does not
-                    # have any device set
-                    try:
-                        list_devices.append(next(module.parameters()).device.index)
-                    except BaseException:
-                        continue
-            return list_devices
-
-        list_devices = get_list_devices(model_parallel)
-        # Check that we have dispatched the model into 2 separate devices
-        self.assertTrue((1 in list_devices) and (0 in list_devices))
+        # Check correct device map
+        self.assertEqual(set(model_parallel.hf_device_map.values()), {0, 1})
 
         # Check that inference pass works on the model
         encoded_input = self.tokenizer(self.input_text, return_tensors="pt")