Override copy method in LazyMetadataDict

The standard implementation of copy results in an empty dict

PiperOrigin-RevId: 696161577

Author: tomvdw

tensorflow_datasets/core/dataset_info.py

@@ -34,6 +34,7 @@
 
 import abc
 from collections.abc import Iterable, Sequence
+import copy
 import dataclasses
 import json
 import os
@@ -1435,6 +1436,9 @@ def items(self):
     self._load_metadata()
     return super().items()
 
+  def copy(self):
+    return copy.deepcopy(self)
+
 
 class BeamMetadataDict(MetadataDict):
   """A `tfds.core.Metadata` object supporting Beam-generated datasets."""

tensorflow_datasets/core/dataset_info_test.py

@@ -889,6 +889,11 @@ def test_updating_before_loading(self, mock_load_metadata_from_file):
     metadata_dict.update({"abc": "def", "ghi": "jkl"})
     mock_load_metadata_from_file.assert_not_called()
 
+  def test_copy(self):
+    metadata_dict = dataset_info.LazyMetadataDict(self.data_dir)
+    metadata_dict_copy = metadata_dict.copy()
+    self.assertEqual(metadata_dict_copy["test"], "test123")
+
 
 if __name__ == "__main__":
   testing.test_main()