diff --git a/bd2fs.py b/bd2fs.py
index 99db366..bc9223a 100644
--- a/bd2fs.py
+++ b/bd2fs.py
@@ -1,7 +1,6 @@
 from pathlib import Path
 
 import grpc
-
 from csi import csi_pb2, csi_pb2_grpc
 from csi.csi_pb2 import (
     NodeStageVolumeRequest,
@@ -30,7 +29,7 @@ def get_fs(request):
 
 
 class Bd2FsIdentityServicer(csi_pb2_grpc.IdentityServicer):
-    def __init__(self, bds):
+    def __init__(self, bds: csi_pb2_grpc.IdentityServicer):
         self.bds = bds
 
     @log_grpc_request
@@ -47,7 +46,7 @@ class Bd2FsIdentityServicer(csi_pb2_grpc.IdentityServicer):
 
 
 class Bd2FsNodeServicer(csi_pb2_grpc.NodeServicer):
-    def __init__(self, bds):
+    def __init__(self, bds: csi_pb2_grpc.NodeServicer):
         self.bds = bds
 
     # @log_grpc_request
@@ -167,7 +166,7 @@ class Bd2FsNodeServicer(csi_pb2_grpc.NodeServicer):
 
 
 class Bd2FsControllerServicer(csi_pb2_grpc.ControllerServicer):
-    def __init__(self, bds):
+    def __init__(self, bds: csi_pb2_grpc.ControllerServicer):
         self.bds = bds
 
     @log_grpc_request