Explicitly set reduction

Author: simonreise

segmentation_models_pytorch/losses/focal.py

@@ -45,6 +45,7 @@ def __init__(
 
         self.mode = mode
         self.ignore_index = ignore_index
+        self.reduction = reduction
         self.focal_loss_fn = partial(
             focal_loss_with_logits,
             alpha=alpha,