Lint + update

visualizer/stats_computer.py

@@ -1,3 +1,5 @@
+"""Statistics computation utilities for the visualizer."""
+
 from collections import defaultdict
 from datetime import datetime, timedelta
 import statistics
@@ -215,4 +217,4 @@ def compute_weekday_hour_heatmap(rows: Iterable[Row]) -> Dict:
     return {
         "grid": heatmap,
         "days_seen": [len(s) for s in weekday_days_seen],
-    }
+    }