Do not try to download and prepare a dataset if it's a read only builder

PiperOrigin-RevId: 718870723

Author: tomvdw

tensorflow_datasets/core/load.py

@@ -501,6 +501,9 @@ def _download_and_prepare_builder(
     download_and_prepare_kwargs: Optional[dict[str, Any]],
 ) -> None:
   """Downloads and prepares the dataset builder if necessary."""
+  if isinstance(dbuilder, read_only_builder.ReadOnlyBuilder):
+    # read only builder can't be used to download and prepare datasets.
+    return
   if dbuilder.is_prepared():
     if not download_and_prepare_kwargs:
       return

tensorflow_datasets/core/utils/version_test.py

@@ -23,6 +23,7 @@
 class VersionTest(testing.TestCase):
 
   def test_str_to_version(self):
+    self.assertEqual(version._str_to_version('0.0.0'), (0, 0, 0))
     self.assertEqual(version._str_to_version('1.2.3'), (1, 2, 3))
     self.assertEqual(version._str_to_version('1.2.*', True), (1, 2, '*'))
     self.assertEqual(version._str_to_version('1.*.3', True), (1, '*', 3))