fix panoptic

Author: Matt Sokoloff

labelbox/data/serialization/coco/panoptic_dataset.py

@@ -131,7 +131,7 @@ def from_common(cls,
 
         for result in results:
             images.append(result[0])
-            all_coco_annotations.extend(result[1])
+            all_coco_annotations.append(result[1])
             coco_categories.update(result[2])
             coco_things.update(result[3])