Update mmod2.py

mmod2.py

@@ -73,8 +73,10 @@ class Mmod2(datasets.GeneratorBasedBuilder):
       ),
     ]
 
-  def _generate_examples(self, images, metadata_path):
+  def _generate_examples(self, images, metadata_path=None, split_key="train"):
     """Generate images and labels for splits."""
+
+    metadata_path = "validation.txt" if split_key == "validation" else "train.txt"
     with open(metadata_path, encoding="utf-8") as f:
       files_to_keep = set(f.read().split("\n"))