fix ugly rendering of 'omit' in UI due to incorrect strip (#2057)

## Problem

  LangSmith UI was showing ugly serialized objects like:
  "seed": "<openai.Omit object at 0x105d91940>",
  "stop": "<openai.Omit object at 0x105d91940>",

<img width="1488" height="755" alt="image"
src="https://github.com/user-attachments/assets/68ae5b0b-fd5e-4686-b3f6-64a11a7b840e"
/>

  This happened because OpenAI SDK v1.106+ uses both NotGiven and
  Omit sentinel types to represent optional parameters that weren't
  provided, but the code only checked for NotGiven.


after fix: 
<img width="1488" height="755" alt="image"
src="https://github.com/user-attachments/assets/26cb7201-af47-4293-af11-d8a16e3c7cd6"
/>

Author: EugeneJinXin

python/langsmith/wrappers/_openai.py

@@ -35,24 +35,29 @@
 
 
 @functools.lru_cache
-def _get_not_given() -> Optional[type]:
+def _get_omit_types() -> tuple[type, ...]:
+    """Get NotGiven/Omit sentinel types used by OpenAI SDK."""
+    types = []
     try:
-        from openai._types import NotGiven
+        from openai._types import NotGiven, Omit
 
-        return NotGiven
+        types.append(NotGiven)
+        types.append(Omit)
     except ImportError:
-        return None
+        pass
+
+    return tuple(types)
 
 
 def _strip_not_given(d: dict) -> dict:
     try:
-        not_given = _get_not_given()
-        if not_given is None:
+        omit_types = _get_omit_types()
+        if not omit_types:
             return d
         return {
             k: v
             for k, v in d.items()
-            if not (isinstance(v, not_given) or (k.startswith("extra_") and v is None))
+            if not (isinstance(v, omit_types) or (k.startswith("extra_") and v is None))
         }
     except Exception as e:
         logger.error(f"Error stripping NotGiven: {e}")

python/tests/integration_tests/wrappers/test_azure_openai.py

@@ -34,14 +34,14 @@ def test_chat_sync_api(stream: bool):
     )
     messages = [{"role": "user", "content": "Say 'foo'"}]
     original = original_client.chat.completions.create(
-        messages=messages,  # noqa: [arg-type]
+        messages=messages,  # noqa: arg-type
         stream=stream,
         temperature=0,
         seed=42,
         model="gpt-4o-mini",
     )
     patched = patched_client.chat.completions.create(
-        messages=messages,  # noqa: [arg-type]
+        messages=messages,  # noqa: arg-type
         stream=stream,
         temperature=0,
         seed=42,

python/tests/integration_tests/wrappers/test_openai.py

@@ -23,14 +23,14 @@ def test_chat_sync_api(stream: bool):
     patched_client = wrap_openai(openai.Client(), tracing_extra={"client": client})
     messages = [{"role": "user", "content": "Say 'foo'"}]
     original = original_client.chat.completions.create(
-        messages=messages,  # noqa: [arg-type]
+        messages=messages,  # noqa: arg-type
         stream=stream,
         temperature=0,
         seed=42,
         model="gpt-3.5-turbo",
     )
     patched = patched_client.chat.completions.create(
-        messages=messages,  # noqa: [arg-type]
+        messages=messages,  # noqa: arg-type
         stream=stream,
         temperature=0,
         seed=42,