diff --git a/src/cehrbert/models/hf_models/tokenization_hf_cehrbert.py b/src/cehrbert/models/hf_models/tokenization_hf_cehrbert.py
index b51cbc38..783007b7 100644
--- a/src/cehrbert/models/hf_models/tokenization_hf_cehrbert.py
+++ b/src/cehrbert/models/hf_models/tokenization_hf_cehrbert.py
@@ -84,6 +84,10 @@ def __init__(
     def vocab_size(self):
         return self._tokenizer.get_vocab_size()
 
+    @property
+    def oov_token_index(self):
+        return self._oov_token_index
+
     @property
     def mask_token_index(self):
         return self._mask_token_index
diff --git a/src/cehrbert/runners/runner_util.py b/src/cehrbert/runners/runner_util.py
index 9ee87c38..d2b7bad8 100644
--- a/src/cehrbert/runners/runner_util.py
+++ b/src/cehrbert/runners/runner_util.py
@@ -19,7 +19,7 @@
 
 
 def load_parquet_as_dataset(
-    data_folder, split="train", streaming=False
+        data_folder, split="train", streaming=False
 ) -> Union[Dataset, IterableDataset]:
     """
     Loads a dataset from Parquet files located within a specified folder into a Hugging Face `datasets.Dataset`.
@@ -101,14 +101,14 @@ def get_last_hf_checkpoint(training_args):
     last_checkpoint = None
     output_dir_abspath = os.path.abspath(training_args.output_dir)
     if (
-        os.path.isdir(output_dir_abspath)
-        and training_args.do_train
-        and not training_args.overwrite_output_dir
+            os.path.isdir(output_dir_abspath)
+            and training_args.do_train
+            and not training_args.overwrite_output_dir
     ):
         last_checkpoint = get_last_checkpoint(output_dir_abspath)
         if (
-            last_checkpoint is None
-            and len([_ for _ in os.listdir(output_dir_abspath) if os.path.isdir(_)]) > 0
+                last_checkpoint is None
+                and len([_ for _ in os.listdir(output_dir_abspath) if os.path.isdir(_)]) > 0
         ):
             raise ValueError(
                 f"Output directory ({output_dir_abspath}) already exists and is not empty. "
@@ -196,28 +196,28 @@ def generate_prepared_ds_path(data_args, model_args, data_folder=None) -> Path:
     """
     data_folder = data_folder if data_folder else data_args.data_folder
     concatenated_str = (
-        str(model_args.max_position_embeddings)
-        + "|"
-        + os.path.abspath(data_folder)
-        + "|"
-        + os.path.abspath(model_args.tokenizer_name_or_path)
-        + "|"
-        + (
-            str(data_args.validation_split_percentage)
-            if data_args.validation_split_percentage
-            else ""
-        )
-        + "|"
-        + f"test_eval_ratio={str(data_args.test_eval_ratio)}"
-        + "|"
-        + f"split_by_patient={str(data_args.split_by_patient)}"
-        + "|"
-        + f"chronological_split={str(data_args.chronological_split)}"
+            str(model_args.max_position_embeddings)
+            + "|"
+            + os.path.abspath(data_folder)
+            + "|"
+            + os.path.abspath(model_args.tokenizer_name_or_path)
+            + "|"
+            + (
+                str(data_args.validation_split_percentage)
+                if data_args.validation_split_percentage
+                else ""
+            )
+            + "|"
+            + f"test_eval_ratio={str(data_args.test_eval_ratio)}"
+            + "|"
+            + f"split_by_patient={str(data_args.split_by_patient)}"
+            + "|"
+            + f"chronological_split={str(data_args.chronological_split)}"
     )
     basename = os.path.basename(data_folder)
     cleaned_basename = re.sub(r"[^a-zA-Z0-9_]", "", basename)
     LOG.info(f"concatenated_str: {concatenated_str}")
-    ds_hash = f"{cleaned_basename}_{str(md5(concatenated_str, usedforsecurity=False))}"
+    ds_hash = f"{cleaned_basename}_{str(md5(concatenated_str))}"
     LOG.info(f"ds_hash: {ds_hash}")
     prepared_ds_path = Path(os.path.abspath(data_args.dataset_prepared_path)) / ds_hash
     return prepared_ds_path
diff --git a/tests/unit_tests/models/hf_models/tokenization_hf_cehrbert_test.py b/tests/unit_tests/models/hf_models/tokenization_hf_cehrbert_test.py
index ddc5ffa3..c8c74345 100644
--- a/tests/unit_tests/models/hf_models/tokenization_hf_cehrbert_test.py
+++ b/tests/unit_tests/models/hf_models/tokenization_hf_cehrbert_test.py
@@ -58,7 +58,7 @@ def test_convert_tokens_to_string(self):
     def test_oov_token(self):
         # Test the encoding of an out-of-vocabulary token
         encoded = self.tokenizer.encode(["nonexistent"])
-        self.assertEqual(encoded, [self.tokenizer._oov_token_index])
+        self.assertEqual(encoded, [self.tokenizer.oov_token_index])
 
     def test_convert_id_to_token_oov(self):
         # Test decoding an out-of-vocabulary token ID