[GraphBolt] Eliminate test warning (#7044)

python/dgl/graphbolt/impl/torch_based_feature_store.py

@@ -72,6 +72,7 @@ class TorchBasedFeature(Feature):
 
     def __init__(self, torch_feature: torch.Tensor, metadata: Dict = None):
         super().__init__()
+        self._is_inplace_pinned = set()
         assert isinstance(torch_feature, torch.Tensor), (
             f"torch_feature in TorchBasedFeature must be torch.Tensor, "
             f"but got {type(torch_feature)}."
@@ -83,7 +84,6 @@ class TorchBasedFeature(Feature):
         # Make sure the tensor is contiguous.
         self._tensor = torch_feature.contiguous()
         self._metadata = metadata
-        self._is_inplace_pinned = set()
 
     def __del__(self):
         # torch.Tensor.pin_memory() is not an inplace operation. To make it