diff --git a/fin_depo/data.py b/fin_depo/data.py
index 4d68124..d0aed92 100644
--- a/fin_depo/data.py
+++ b/fin_depo/data.py
@@ -71,8 +71,10 @@ class DepoGroup(Depo):
             del nested_depo
         return summed
 
+
 T = TypeVar('T')
 
+
 class DepoFetcher(abc.ABC):
     """Base `Depo` fetcher interface.
 
diff --git a/fin_depo/defi_kraken.py b/fin_depo/defi_kraken.py
index d5335bd..2cedacc 100644
--- a/fin_depo/defi_kraken.py
+++ b/fin_depo/defi_kraken.py
@@ -7,7 +7,7 @@ from decimal import Decimal
 import fin_defs
 import krakenex
 
-from .data import Depo, DepoSingle, DepoFetcher
+from .data import Depo, DepoFetcher, DepoSingle
 
 logger = logging.getLogger(__name__)
 
@@ -29,8 +29,6 @@ class KrakenDepoFetcher(DepoFetcher):
     def __init__(self, kraken_key: str, kraken_secret: str):
         self.assert_param('kraken_key', str, kraken_key)
         self.assert_param('kraken_secret', str, kraken_secret)
-        assert kraken_key is not None, 'Missing kraken_key'
-        assert kraken_secret is not None, 'Missing kraken_secret'
         self.client = krakenex.API(
             kraken_key,
             kraken_secret,
@@ -42,13 +40,13 @@ class KrakenDepoFetcher(DepoFetcher):
         result = self.client.query_private('Balance')
 
         assets: dict[fin_defs.Asset, Decimal] = {}
-        for account, balance_str in result['result'].items():
-            account = account.removesuffix('.HOLD')
+        for account_raw, balance_str in result['result'].items():
+            account = account_raw.removesuffix('.HOLD')
             asset = fin_defs.WELL_KNOWN_SYMBOLS[account]
             balance = Decimal(balance_str)
             if balance != 0:
                 assets[asset] = assets.get(asset, Decimal(0)) + balance
-            del account, balance_str, asset, balance
+            del account, account_raw, balance_str, asset, balance
 
         return DepoSingle(
             name='Kraken',
diff --git a/fin_depo/defi_kucoin.py b/fin_depo/defi_kucoin.py
index 5d6b976..da4f8df 100644
--- a/fin_depo/defi_kucoin.py
+++ b/fin_depo/defi_kucoin.py
@@ -7,7 +7,7 @@ from decimal import Decimal
 import fin_defs
 import kucoin.client
 
-from .data import DepoGroup, DepoSingle, DepoFetcher
+from .data import DepoFetcher, DepoGroup, DepoSingle
 
 logger = logging.getLogger(__name__)
 
diff --git a/fin_depo/defi_partisia_blockchain.py b/fin_depo/defi_partisia_blockchain.py
index 09b7aa4..337d904 100644
--- a/fin_depo/defi_partisia_blockchain.py
+++ b/fin_depo/defi_partisia_blockchain.py
@@ -2,7 +2,6 @@
 
 import dataclasses
 import datetime
-import requests
 import email.utils
 import json
 import logging
@@ -13,7 +12,7 @@ import fin_defs
 import requests
 from frozendict import frozendict
 
-from .data import DepoGroup, DepoSingle, DepoFetcher
+from .data import DepoFetcher, DepoGroup, DepoSingle
 
 logger = logging.getLogger(__name__)
 
diff --git a/fin_depo/investbank_nordnet.py b/fin_depo/investbank_nordnet.py
index 8cadd6e..3dd12fd 100644
--- a/fin_depo/investbank_nordnet.py
+++ b/fin_depo/investbank_nordnet.py
@@ -11,13 +11,13 @@ I am grateful for his pioneering work.
 
 import datetime
 import logging
-import requests
 from decimal import Decimal
 
 import fin_defs
+import requests
 from frozendict import frozendict
 
-from .data import Depo, DepoGroup, DepoSingle, DepoFetcher
+from .data import Depo, DepoFetcher, DepoGroup, DepoSingle
 
 logger = logging.getLogger(__name__)
 
@@ -40,7 +40,9 @@ def asset_from_instrument_json(json) -> fin_defs.Asset | None:
     exchange_id = json['tradables'][0]['mic']
     return fin_defs.Stock(symbol, fin_defs.EXCHANGES_BY_IDS[exchange_id])
 
-EMPTY_DICT: dict[str,str | int] = frozendict()
+
+EMPTY_DICT: dict[str, str | int] = frozendict()
+
 
 class NordnetDepoFetcher(DepoFetcher):
     """Depository fetcher for [Nordnet](https://nordnet.dk), the online investment bank.
@@ -59,13 +61,12 @@ class NordnetDepoFetcher(DepoFetcher):
     """
 
     def __init__(self, session: requests.Session, username: str, password: str):
-
         self.session = self.assert_param('session', requests.Session, session)
         self.username: str = self.assert_param('username', str, username)
         self.password: str = self.assert_param('password', str, password)
         self.is_logged_in = False
 
-    def _get_json(self, url: str, params: dict[str, str | int] = EMPTY_DICT)-> dict:
+    def _get_json(self, url: str, params: dict[str, str | int] = EMPTY_DICT) -> dict:
         if not url.startswith(API_ROOT):
             msg = f'Given url must be located below API ROOT: {url}'
             raise ValueError(msg)