Add the detach method.

src/tensor.rs

@@ -524,6 +524,22 @@ impl Tensor {
         Ok(Tensor(Arc::new(tensor_)))
     }
 
+    // TODO: Currently this duplicates the storage, the PyTorch version would share the storage,
+    // maybe we should do the same?
+    /// Returns a new tensor detached from the current graph, gradient are not propagated through
+    /// this new node.
+    pub fn detach(&self) -> Result<Tensor> {
+        let tensor_ = Tensor_ {
+            id: TensorId::new(),
+            storage: self.storage.try_clone()?,
+            shape: self.shape.clone(),
+            stride: self.stride.clone(),
+            op: None,
+            is_variable: false,
+        };
+        Ok(Tensor(Arc::new(tensor_)))
+    }
+
     /// If the target device is the same as the tensor device, only a shallow copy is performed.
     pub fn to_device(&self, device: &Device) -> Result<Tensor> {
         if self.device().same_id(device) {