Add comments to explain why we use model.call.

PiperOrigin-RevId: 371837967

official/vision/beta/serving/detection.py

@@ -120,6 +120,9 @@ class DetectionModule(export_base.ExportModule):
 
     input_image_shape = image_info[:, 1, :]
 
+    # To overcome keras.Model extra limitation to save a model with layers that
+    # have multiple inputs, we use `model.call` here to trigger the forward
+    # path. Note that, this disables some keras magics happens in `__call__`.
     detections = self.model.call(
         images=images,
         image_shape=input_image_shape,