fixing linter

Author: maeste

src/a2a/server/apps/jsonrpc/jsonrpc_app.py

@@ -5,9 +5,9 @@
 
 from abc import ABC, abstractmethod
 from collections.abc import AsyncGenerator, Callable
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, Type
 
-from pydantic import ValidationError
+from pydantic import BaseModel, ValidationError
 
 from a2a.auth.user import UnauthenticatedUser
 from a2a.auth.user import User as A2AUser
@@ -156,7 +156,7 @@ class JSONRPCApplication(ABC):
     """
 
     # Method-to-model mapping for centralized routing
-    METHOD_TO_MODEL = {
+    METHOD_TO_MODEL: dict[str, Type[BaseModel]] = {
         'message/send': SendMessageRequest,
         'message/stream': SendStreamingMessageRequest,
         'tasks/get': GetTaskRequest,