diff --git a/mesa/agent.py b/mesa/agent.py
index 1a7c24d42af..acc40cc9b1e 100644
--- a/mesa/agent.py
+++ b/mesa/agent.py
@@ -358,9 +358,7 @@ def random(self) -> Random:
         """
         return self.model.random
 
-    def group_by(
-        self, by: Callable | str, result_type: str = "agentset"
-    ) -> GroupBy:
+    def group_by(self, by: Callable | str, result_type: str = "agentset") -> GroupBy:
         """
         Group agents by the specified attribute