Update src/torchmetrics/functional/segmentation/utils.py

Co-authored-by: Jirka Borovec <6035284+Borda@users.noreply.github.com>

src/torchmetrics/functional/segmentation/utils.py

@@ -25,7 +25,7 @@
 
 
 def _ignore_background(preds: Tensor, target: Tensor) -> Tuple[Tensor, Tensor]:
-    """Ignore the background class in the computation."""
+    """Ignore the background class in the computation assuming it is the first, index 0."""
     preds = preds[:, 1:] if preds.shape[1] > 1 else preds
     target = target[:, 1:] if target.shape[1] > 1 else target
     return preds, target