Fix: make y optional in ignore_background

Signed-off-by: Tristan Kirscher <85068746+Kirscher@users.noreply.github.com>

Author: Kirscher

monai/metrics/active_learning_metrics.py

@@ -129,9 +129,7 @@ def compute_variance(
     y_pred = y_pred.float()
 
     if not include_background:
-        y = y_pred
-        # TODO If this utils is made to be optional for 'y' it would be nice
-        y_pred, y = ignore_background(y_pred=y_pred, y=y)
+        y_pred, _ = ignore_background(y_pred=y_pred, y=None)
 
     # Set any values below 0 to threshold
     y_pred[y_pred <= 0] = threshold

monai/metrics/utils.py

@@ -51,7 +51,9 @@
 ]
 
 
-def ignore_background(y_pred: NdarrayTensor, y: NdarrayTensor) -> tuple[NdarrayTensor, NdarrayTensor]:
+def ignore_background(
+    y_pred: NdarrayTensor, y: NdarrayTensor | None = None
+) -> tuple[NdarrayTensor, NdarrayTensor | None]:
     """
     This function is used to remove background (the first channel) for `y_pred` and `y`.
 
@@ -63,7 +65,8 @@ def ignore_background(y_pred: NdarrayTensor, y: NdarrayTensor) -> tuple[NdarrayT
 
     """
 
-    y = y[:, 1:] if y.shape[1] > 1 else y  # type: ignore[assignment]
+    if y is not None:
+        y = y[:, 1:] if y.shape[1] > 1 else y  # type: ignore[assignment]
     y_pred = y_pred[:, 1:] if y_pred.shape[1] > 1 else y_pred  # type: ignore[assignment]
     return y_pred, y