diff --git a/rasa/nlu/training_data/training_data.py b/rasa/nlu/training_data/training_data.py
index 6ac11824f8d9..787f63a5a734 100644
--- a/rasa/nlu/training_data/training_data.py
+++ b/rasa/nlu/training_data/training_data.py
@@ -16,6 +16,7 @@
 from rasa.nlu.training_data.message import Message
 from rasa.nlu.training_data.util import check_duplicate_synonym
 from rasa.nlu.utils import list_to_str
+from sklearn.model_selection import train_test_split
 
 DEFAULT_TRAINING_DATA_OUTPUT_PATH = "training_data.json"
 
@@ -349,6 +350,7 @@ def train_test_split(
         preserving the fraction of examples per intent."""
 
         # collect all nlu data
+
         test, train = self.split_nlu_examples(train_frac, random_seed)
 
         # collect all nlg stories
@@ -395,6 +397,7 @@ def build_nlg_stories_from_examples(examples) -> Dict[Text, list]:
                 ]
         return nlg_stories
 
+
     def split_nlu_examples(
         self, train_frac: float, random_seed: Optional[int] = None
     ) -> Tuple[list, list]: