Filter our unrecognized `image_classes_field` entries (i.e -1s)

PiperOrigin-RevId: 336321500

research/object_detection/inputs.py

@@ -88,7 +88,8 @@ def _convert_labeled_classes_to_k_hot(groundtruth_labeled_classes, num_classes):
 def _remove_unrecognized_classes(class_ids, unrecognized_label):
   """Returns class ids with unrecognized classes filtered out."""
 
-  recognized_indices = tf.where(tf.greater(class_ids, unrecognized_label))
+  recognized_indices = tf.squeeze(
+      tf.where(tf.greater(class_ids, unrecognized_label)), -1)
   return tf.gather(class_ids, recognized_indices)
 
 
@@ -213,6 +214,8 @@ def transform_input_data(tensor_dict,
         out_tensor_dict[labeled_classes_field], num_classes)
 
   if image_classes_field in out_tensor_dict:
+    out_tensor_dict[image_classes_field] = _remove_unrecognized_classes(
+        out_tensor_dict[image_classes_field], unrecognized_label=-1)
     out_tensor_dict[labeled_classes_field] = _convert_labeled_classes_to_k_hot(
         out_tensor_dict[image_classes_field], num_classes)