Merged commit includes the following changes: (#8742)

318569851  by jonathanhuang:

    Fix for fine-tuning from classification checkpoints in the v2 binary.

--

PiperOrigin-RevId: 318569851

research/object_detection/meta_architectures/faster_rcnn_meta_arch.py

@@ -2801,7 +2801,10 @@ class FasterRCNNMetaArch(model.DetectionModel):
       A dict mapping keys to Trackable objects (tf.Module or Checkpoint).
     """
     if fine_tune_checkpoint_type == 'classification':
-      return {'feature_extractor': self.classification_backbone}
+      return {
+          'feature_extractor':
+              self._feature_extractor.classification_backbone
+      }
     elif fine_tune_checkpoint_type == 'detection':
       fake_model = tf.train.Checkpoint(
           _feature_extractor_for_box_classifier_features=

research/object_detection/meta_architectures/ssd_meta_arch.py

@@ -1320,7 +1320,10 @@ class SSDMetaArch(model.DetectionModel):
       A dict mapping keys to Trackable objects (tf.Module or Checkpoint).
     """
     if fine_tune_checkpoint_type == 'classification':
-      return {'feature_extractor': self.classification_backbone}
+      return {
+          'feature_extractor':
+              self._feature_extractor.classification_backbone
+      }
     elif fine_tune_checkpoint_type == 'detection':
       fake_model = tf.train.Checkpoint(
           _feature_extractor=self._feature_extractor)