chore: export NOT_GIVEN sentinel value (openai#1223)

Author: stainless-bot

src/openai/__init__.py

@@ -6,7 +6,7 @@
 from typing_extensions import override
 
 from . import types
-from ._types import NoneType, Transport, ProxiesTypes
+from ._types import NOT_GIVEN, NoneType, NotGiven, Transport, ProxiesTypes
 from ._utils import file_from_path
 from ._client import Client, OpenAI, Stream, Timeout, Transport, AsyncClient, AsyncOpenAI, AsyncStream, RequestOptions
 from ._models import BaseModel
@@ -37,6 +37,8 @@
     "NoneType",
     "Transport",
     "ProxiesTypes",
+    "NotGiven",
+    "NOT_GIVEN",
     "OpenAIError",
     "APIError",
     "APIStatusError",