Update label_tensor.py cpu/gpu (#292)

* Update label_tensor.py cpu/gpu
* Update test_adaptive_refinment_callbacks.py
* Update test_optimizer_callbacks.py

pina/label_tensor.py

@@ -176,7 +176,7 @@ class LabelTensor(torch.Tensor):
         tmp = super().cuda(*args, **kwargs)
         new = self.__class__.clone(self)
         new.data = tmp.data
-        return tmp
+        return new
 
     def cpu(self, *args, **kwargs):
         """
@@ -185,7 +185,7 @@ class LabelTensor(torch.Tensor):
         tmp = super().cpu(*args, **kwargs)
         new = self.__class__.clone(self)
         new.data = tmp.data
-        return tmp
+        return new
 
     def extract(self, label_to_extract):
         """