fix toolset codes to make it work with python 3.9

PiperOrigin-RevId: 757991503

src/google/adk/tools/apihub_tool/apihub_toolset.py

@@ -15,9 +15,9 @@
 
 from typing import List
 from typing import Optional
-from typing import override
 from typing import Union
 
+from typing_extensions import override
 import yaml
 
 from ...agents.readonly_context import ReadonlyContext

src/google/adk/tools/application_integration_tool/application_integration_toolset.py

@@ -14,10 +14,10 @@
 
 from typing import List
 from typing import Optional
-from typing import override
 from typing import Union
 
 from fastapi.openapi.models import HTTPBearer
+from typing_extensions import override
 
 from ...auth.auth_credential import AuthCredential
 from ...auth.auth_credential import AuthCredentialTypes

src/google/adk/tools/google_api_tool/google_api_tool_set.py

@@ -19,10 +19,11 @@ import os
 from typing import Any
 from typing import List
 from typing import Optional
-from typing import override
 from typing import Type
 from typing import Union
 
+from typing_extensions import override
+
 from ...agents.readonly_context import ReadonlyContext
 from ...auth import OpenIdConnectWithConfig
 from ...tools.base_toolset import BaseToolset

src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_toolset.py

@@ -20,9 +20,9 @@ from typing import Final
 from typing import List
 from typing import Literal
 from typing import Optional
-from typing import override
 from typing import Union
 
+from typing_extensions import override
 import yaml
 
 from ....agents.readonly_context import ReadonlyContext
@@ -101,7 +101,7 @@ class OpenAPIToolset(BaseToolset):
         AuthCredential or use helpers in
         `google.adk.tools.openapi_tool.auth.auth_helpers`
       tool_filter: The filter used to filter the tools in the toolset. It can be
-        either a tool predicate or a list of tool names of the tools to expose
+        either a tool predicate or a list of tool names of the tools to expose.
     """
     if not spec_dict:
       spec_dict = self._load_spec(spec_str, spec_str_type)