minor style elements

research/object_detection/core/box_list_ops.py

@@ -34,6 +34,7 @@ from object_detection.core import box_list
 from object_detection.utils import ops
 from object_detection.utils import shape_utils
 
+
 class SortOrder(object):
   """Enum class for sort order.
 

research/object_detection/core/target_assigner.py

@@ -163,7 +163,6 @@ class TargetAssigner(object):
       ValueError: if anchors or groundtruth_boxes are not of type
         box_list.BoxList
     """
-    
     if not isinstance(anchors, box_list.BoxList):
       raise ValueError('anchors must be an BoxList')
     if not isinstance(groundtruth_boxes, box_list.BoxList):