Fix ruff lint error TC001

Author: holtskinner

src/a2a/client/legacy_grpc.py

@@ -2,17 +2,22 @@
 
 import warnings
 
+from typing import TYPE_CHECKING
+
 from a2a.client.transports.grpc import GrpcTransport
-from a2a.grpc import a2a_pb2_grpc
 from a2a.types import AgentCard
 
 
+if TYPE_CHECKING:
+    from a2a.grpc.a2a_pb2_grpc import A2AServiceStub
+
+
 class A2AGrpcClient(GrpcTransport):
     """[DEPRECATED] Backwards compatibility wrapper for the gRPC client."""
 
     def __init__(
         self,
-        grpc_stub: 'a2a_pb2_grpc.A2AServiceStub',
+        grpc_stub: 'A2AServiceStub',
         agent_card: AgentCard,
     ):
         warnings.warn(