diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index 2808ffb..74df416 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -6216,8 +6216,10 @@ class TestApi:
 
         self.leave(p)
 
+
     # 37 virtual_district
 
+
     def test_virtual_district(self):
         p = 'test_virtual_district'
         read_inp(p, f'./inp/net3.inp', '3')
diff --git a/tjnetwork.py b/tjnetwork.py
index 7c2fc73..0517260 100644
--- a/tjnetwork.py
+++ b/tjnetwork.py
@@ -1008,6 +1008,5 @@ def distribute_demand_to_region(name: str, demand: float, region: str, type: str
 # virtual_district 37
 ############################################################
 
-# parent is whole network
-def calculate_virtual_district(name: str, centers: list[str]) -> dict[str, Any]:
+def calculate_virtual_district(name: str, centers: list[str]) -> dict[str, list[Any]]:
     return api.calculate_virtual_district(name, centers)