# _NULL_SENTRY

> **Class** in `langsmith`

📖 [View in docs](https://reference.langchain.com/python/langsmith/_expect/_NULL_SENTRY)

A sentinel singleton class used to distinguish omitted keyword arguments
from those passed in with the value None (which may have different behavior).

## Signature

```python
_NULL_SENTRY()
```

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[View source on GitHub](https://github.com/langchain-ai/langsmith-sdk/blob/19dc497a3d89638e4cc35db72ea1c29cad35cbbf/python/langsmith/_expect.py#L76)