Make ClipWindow with Combined work with batch size > 1.

PiperOrigin-RevId: 393480597

research/object_detection/core/post_processing.py

@@ -402,10 +402,10 @@ def _clip_boxes(boxes, clip_window):
     window.
   """
   ymin, xmin, ymax, xmax = tf.unstack(boxes, axis=-1)
-  clipped_ymin = tf.maximum(ymin, clip_window[:, 0])
-  clipped_xmin = tf.maximum(xmin, clip_window[:, 1])
-  clipped_ymax = tf.minimum(ymax, clip_window[:, 2])
-  clipped_xmax = tf.minimum(xmax, clip_window[:, 3])
+  clipped_ymin = tf.maximum(ymin, clip_window[:, 0, tf.newaxis])
+  clipped_xmin = tf.maximum(xmin, clip_window[:, 1, tf.newaxis])
+  clipped_ymax = tf.minimum(ymax, clip_window[:, 2, tf.newaxis])
+  clipped_xmax = tf.minimum(xmax, clip_window[:, 3, tf.newaxis])
   return tf.stack([clipped_ymin, clipped_xmin, clipped_ymax, clipped_xmax],
                   axis=-1)