diff --git a/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py b/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py
index e11d531..21d003d 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/cpu_time.py
@@ -36,7 +36,11 @@ class CpuTimeDataModel(DataModel):
         ])
 
     def add_duration(
-        self, tid: int, start_timestamp: int, duration: int, cpu_id: int
+        self,
+        tid: int,
+        start_timestamp: int,
+        duration: int,
+        cpu_id: int,
     ) -> None:
         data = {
             'tid': tid,