diff --git a/pytorch_to_returnn/torch/fft.py b/pytorch_to_returnn/torch/fft.py
new file mode 100644
index 0000000..e69de29
diff --git a/pytorch_to_returnn/torch/tensor.py b/pytorch_to_returnn/torch/tensor.py
index 1e50ac6..4ee6ee0 100644
--- a/pytorch_to_returnn/torch/tensor.py
+++ b/pytorch_to_returnn/torch/tensor.py
@@ -98,15 +98,18 @@ def clone(self):
   def cpu(self):
     return self  # ignore
 
+  def cuda(self):
+    return self  # ignore
+
   @property
   def device(self):
     class DeviceDummy:
       type = None
     return DeviceDummy()
 
-  def flatten(self):
+  def flatten(self, start_dim=0, end_dim=-1):
     from .nn.functional import flatten
-    return flatten(self)
+    return flatten(self, start_dim, end_dim)
 
   def view(self, *shape):
     from .nn.functional import reshape