diff --git a/returnn/datasets/meta.py b/returnn/datasets/meta.py
index 5da60c8535..ab9c4230e9 100644
--- a/returnn/datasets/meta.py
+++ b/returnn/datasets/meta.py
@@ -23,6 +23,7 @@
 
 from __future__ import annotations
 
+from typing import List
 from returnn.datasets.basic import Dataset, DatasetSeq, init_dataset, convert_data_dims
 from .cached2 import CachedDataset2
 from returnn.util.basic import NumbersDict, load_json
@@ -533,6 +534,10 @@ def get_tag(self, sorted_seq_idx):
         """
         return self.seq_list_ordered[self.default_dataset_key][sorted_seq_idx]
 
+    def get_data_keys(self) -> List[str]:
+        """data keys"""
+        return sorted(self.data_keys)
+
     def get_target_list(self):
         """
         :rtype: list[str]