fix extended coco load missing comma

Summary: Fix missing comma for extended coco load, which would ignore bbox_mode and keypoints field.

Reviewed By: zhanghang1989

Differential Revision: D29608815

fbshipit-source-id: 8c737df1dfef7f88494f7de25e06b0c37742ac30

d2go/data/extended_coco.py

@@ -178,7 +178,7 @@ def convert_to_dict_list(image_root, id_map, imgs, anns, dataset_name=None):
                 for field in [
                     "iscrowd",
                     "bbox",
-                    "bbox_mode"
+                    "bbox_mode",
                     "keypoints",
                     "category_id",
                     "extras",