Don't require image/source_id feature if regenerate_source_id is set.

PiperOrigin-RevId: 395539392

Author: tensorflower-gardener

official/vision/beta/dataloaders/tf_example_decoder.py

@@ -38,7 +38,6 @@ def __init__(self,
     self._regenerate_source_id = regenerate_source_id
     self._keys_to_features = {
         'image/encoded': tf.io.FixedLenFeature((), tf.string),
-        'image/source_id': tf.io.FixedLenFeature((), tf.string),
         'image/height': tf.io.FixedLenFeature((), tf.int64),
         'image/width': tf.io.FixedLenFeature((), tf.int64),
         'image/object/bbox/xmin': tf.io.VarLenFeature(tf.float32),
@@ -54,6 +53,10 @@ def __init__(self,
       self._keys_to_features.update({
           'image/object/mask': tf.io.VarLenFeature(tf.string),
       })
+    if not regenerate_source_id:
+      self._keys_to_features.update({
+          'image/source_id': tf.io.FixedLenFeature((), tf.string),
+      })
 
   def _decode_image(self, parsed_tensors):
     """Decodes the image and set its static shape."""