[model] Fix detection of binary targets in loss balancing

src/mednet/models/loss_weights.py

@@ -162,7 +162,7 @@ def get_positive_weights(
 
     targets_tensor = torch.tensor(targets_list)
 
-    if len(list(targets_tensor.shape)) == 1:
+    if targets_tensor.shape[0] == 1:
         logger.info("Computing positive weights assuming binary labels.")
         positive_weights = compute_binary_weights(targets_tensor)
     else: