code: def test_sub_split_wrong_key(self):
      with self.assertRaisesWithPredicateMatch(
          ValueError, "Unknown split 'unknown'"
      ):
          _ = self._builder.info.splits["unknown"]
  
imports: from tensorflow_datasets import testing
  from tensorflow_datasets.core import naming
  from tensorflow_datasets.core import proto
  from tensorflow_datasets.core import splits
  from tensorflow_datasets.core.utils import shard_utils
  import tensorflow_datasets.public_api
label_desc: Use image node_id 9 for calling the SplitsTest obj's underlying member method code with example usage: obj.test_sub_split_wrong_key() without return types