fix call to db.Region.insert(db.Box)

src/lclayout/writer/lef_writer.py

@@ -54,7 +54,8 @@ def region_to_geometries(region: db.Region, f: float, use_rectangles_only: bool
         # Decompose into rectangles.
         boxes = _decompose_region(region)
         region = db.Region()
-        region.insert(boxes)
+        for box in boxes:
+            region.insert(box)
 
     geometries = []
     for p in region.each():