diff --git a/melusine/_config.py b/melusine/_config.py
index 58eee93..3b94944 100644
--- a/melusine/_config.py
+++ b/melusine/_config.py
@@ -1,6 +1,7 @@
 """
 Module which handles the package configuration.
 """
+
 import copy
 import logging
 import os
diff --git a/melusine/backend/base_backend.py b/melusine/backend/base_backend.py
index 16e88f7..cd5f46a 100644
--- a/melusine/backend/base_backend.py
+++ b/melusine/backend/base_backend.py
@@ -7,6 +7,7 @@
     BaseTransformerBackend,
 ]
 """
+
 from abc import ABC, abstractmethod
 from typing import Any, Callable, List, Optional
 
diff --git a/melusine/backend/pandas_backend.py b/melusine/backend/pandas_backend.py
index 9228d5e..951dc8a 100644
--- a/melusine/backend/pandas_backend.py
+++ b/melusine/backend/pandas_backend.py
@@ -5,6 +5,7 @@
     PandasBackend,
 ]
 """
+
 from typing import Any, Callable, List, Optional, Tuple, Union
 
 import numpy as np
diff --git a/melusine/base.py b/melusine/base.py
index f586db5..a0f72c1 100644
--- a/melusine/base.py
+++ b/melusine/base.py
@@ -11,6 +11,7 @@
     MelusineFeatureEncoder
 ]
 """
+
 from __future__ import annotations
 
 import copy
diff --git a/melusine/connectors/gmail.py b/melusine/connectors/gmail.py
index 8b31c92..682d445 100644
--- a/melusine/connectors/gmail.py
+++ b/melusine/connectors/gmail.py
@@ -11,6 +11,7 @@
 from google.oauth2.credentials import Credentials
 from google_auth_oauthlib.flow import InstalledAppFlow
 from googleapiclient.discovery import build
+from googleapiclient.errors import HttpError
 from tqdm import tqdm
 
 logger = logging.getLogger(__name__)
@@ -158,8 +159,15 @@ def create_label(self, label_name: str) -> Dict[str, str]:
         Returns:
             Dict[str, str]: return from the api with label and its informations
         """
-        label = self.service.users().labels().create(userId="me", body=dict(name=label_name)).execute()
-        logger.info(f"Label {label_name} has been created.")
+        try:
+            label = self.service.users().labels().create(userId="me", body=dict(name=label_name)).execute()
+            logger.info(f"Label {label_name} has been created.")
+        except HttpError as error:
+            if error.resp.status == 409:  # Conflict error if label already exists
+                logger.error(f"Label '{label_name}' already exists.")
+                return {}
+            else:
+                raise
         return label
 
     @staticmethod
diff --git a/melusine/detectors.py b/melusine/detectors.py
index e6a10c7..96bf51a 100644
--- a/melusine/detectors.py
+++ b/melusine/detectors.py
@@ -5,6 +5,7 @@
 ReplyDetector, TransferDetector, RecipientsDetector]
 
 """
+
 from typing import Any, Dict, List, Tuple
 
 from melusine.base import MelusineDetector, MelusineItem, MelusineRegex
diff --git a/melusine/io/_classes.py b/melusine/io/_classes.py
index 02c6c6e..e7c6c24 100644
--- a/melusine/io/_classes.py
+++ b/melusine/io/_classes.py
@@ -3,6 +3,7 @@
 
 Contained classes: [IoMixin]
 """
+
 from __future__ import annotations
 
 import logging
diff --git a/melusine/message.py b/melusine/message.py
index 97d5c01..e58e09f 100644
--- a/melusine/message.py
+++ b/melusine/message.py
@@ -5,6 +5,7 @@
 
 Implemented classes: [Message]
 """
+
 import re
 from datetime import datetime
 from typing import Iterable, List, Optional, Tuple
diff --git a/melusine/pipeline.py b/melusine/pipeline.py
index 6888ae2..7c37dfb 100644
--- a/melusine/pipeline.py
+++ b/melusine/pipeline.py
@@ -3,6 +3,7 @@
 
 Implemented classes: [PipelineConfigurationError, MelusinePipeline]
 """
+
 from __future__ import annotations
 
 import copy
diff --git a/melusine/processors.py b/melusine/processors.py
index 7239bd3..c40e49b 100644
--- a/melusine/processors.py
+++ b/melusine/processors.py
@@ -18,6 +18,7 @@
     Cleaner,
 ]
 """
+
 from __future__ import annotations
 
 import logging
@@ -1901,7 +1902,6 @@ def clean(self, text: str) -> str:
 
 
 class DateProcessor(MelusineTransformer):
-
     """
     Parse string date to iso format string date
     """
diff --git a/melusine/regex/__init__.py b/melusine/regex/__init__.py
index b987cd3..f27b8a8 100644
--- a/melusine/regex/__init__.py
+++ b/melusine/regex/__init__.py
@@ -1,6 +1,7 @@
 """
 The melusine.regex module includes tools for handling regexes.
 """
+
 from melusine.regex.emergency_regex import EmergencyRegex
 from melusine.regex.reply_regex import ReplyRegex
 from melusine.regex.thanks_regex import ThanksRegex
diff --git a/melusine/testing/pipeline_testing.py b/melusine/testing/pipeline_testing.py
index bed25f7..28aa90c 100644
--- a/melusine/testing/pipeline_testing.py
+++ b/melusine/testing/pipeline_testing.py
@@ -1,6 +1,7 @@
 """
 Module that contains utility functions for tests (in /tests).
 """
+
 from typing import Any, Dict
 
 from melusine.base import MelusineTransformer
diff --git a/melusine/utils/__init__.py b/melusine/utils/__init__.py
index 612fb05..13c2efe 100644
--- a/melusine/utils/__init__.py
+++ b/melusine/utils/__init__.py
@@ -1,6 +1,7 @@
 """
 The melusine.utils module includes utils functionalitites.
 """
+
 from melusine.utils.show_versions import show_versions
 
 __all__ = ["show_versions"]
diff --git a/tests/detectors/test_reply_detector.py b/tests/detectors/test_reply_detector.py
index b939fef..56555a2 100644
--- a/tests/detectors/test_reply_detector.py
+++ b/tests/detectors/test_reply_detector.py
@@ -1,6 +1,7 @@
 """
 Unit tests of the ReplyDetector.
 """
+
 import pandas as pd
 import pytest
 from pandas import DataFrame
diff --git a/tests/detectors/test_thanks_detector.py b/tests/detectors/test_thanks_detector.py
index b84510a..7f6e41c 100644
--- a/tests/detectors/test_thanks_detector.py
+++ b/tests/detectors/test_thanks_detector.py
@@ -2,6 +2,7 @@
 Unit test of the ThanksDetector.
 
 """
+
 from tempfile import TemporaryDirectory
 
 import pandas as pd
diff --git a/tests/detectors/test_transfer_detector.py b/tests/detectors/test_transfer_detector.py
index e9ae89f..96ab166 100644
--- a/tests/detectors/test_transfer_detector.py
+++ b/tests/detectors/test_transfer_detector.py
@@ -2,7 +2,6 @@
 Unit tests of the TransferDetector.
 """
 
-
 import pandas as pd
 import pytest
 from pandas import DataFrame
diff --git a/tests/detectors/test_vacation_reply_detector.py b/tests/detectors/test_vacation_reply_detector.py
index d733779..40a625f 100644
--- a/tests/detectors/test_vacation_reply_detector.py
+++ b/tests/detectors/test_vacation_reply_detector.py
@@ -1,6 +1,7 @@
 """
 Unit tests of the VacationReplyDetector
 """
+
 import pandas as pd
 import pytest
 from pandas import DataFrame
diff --git a/tests/functional/test_emails_fixtures.py b/tests/functional/test_emails_fixtures.py
index 30586ab..58f719b 100644
--- a/tests/functional/test_emails_fixtures.py
+++ b/tests/functional/test_emails_fixtures.py
@@ -41,6 +41,7 @@
 }
 ========================================================================================
 """
+
 import pytest
 
 testcase_initial_cleaning_1 = dict(
diff --git a/tests/pipeline/test_pipeline.py b/tests/pipeline/test_pipeline.py
index 507530e..cecb5cd 100644
--- a/tests/pipeline/test_pipeline.py
+++ b/tests/pipeline/test_pipeline.py
@@ -1,6 +1,7 @@
 """
 Unit test for pipeline.py
 """
+
 import pandas as pd
 import pytest
 
diff --git a/tests/pipeline/test_pipeline_basic.py b/tests/pipeline/test_pipeline_basic.py
index 5eb94ae..d2b2f25 100644
--- a/tests/pipeline/test_pipeline_basic.py
+++ b/tests/pipeline/test_pipeline_basic.py
@@ -1,6 +1,7 @@
 """
 Example script to fit a minimal preprocessing pipeline
 """
+
 import pandas as pd
 import pytest
 
diff --git a/tests/processors/test_processors.py b/tests/processors/test_processors.py
index ba4257a..c6aaae5 100644
--- a/tests/processors/test_processors.py
+++ b/tests/processors/test_processors.py
@@ -1,6 +1,7 @@
 """
 Unit test for processors.py
 """
+
 import pytest
 
 from melusine.processors import (