diff --git a/kombu/utils/encoding.py b/kombu/utils/encoding.py
index 32eb9941..2487e6f5 100644
--- a/kombu/utils/encoding.py
+++ b/kombu/utils/encoding.py
@@ -45,8 +45,12 @@ else:
 
 @overload
 def str_to_bytes(s: str) -> bytes: ...
+
+
 @overload
 def str_to_bytes(s: T) -> T: ...
+
+
 def str_to_bytes(s: Any) -> Any:
     """Convert str to bytes."""
     if isinstance(s, str):
@@ -56,8 +60,12 @@ def str_to_bytes(s: Any) -> Any:
 
 @overload
 def bytes_to_str(s: bytes) -> str: ...
+
+
 @overload
 def bytes_to_str(s: T) -> T: ...
+
+
 def bytes_to_str(s: Any) -> Any:
     """Convert bytes to str."""
     if isinstance(s, bytes):