# RetrieverManagerMixin

> **Class** in `langchain_core`

📖 [View in docs](https://reference.langchain.com/python/langchain-core/callbacks/base/RetrieverManagerMixin)

Mixin for `Retriever` callbacks.

## Signature

```python
RetrieverManagerMixin()
```

## Methods

- [`on_retriever_error()`](https://reference.langchain.com/python/langchain-core/callbacks/base/RetrieverManagerMixin/on_retriever_error)
- [`on_retriever_end()`](https://reference.langchain.com/python/langchain-core/callbacks/base/RetrieverManagerMixin/on_retriever_end)

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[View source on GitHub](https://github.com/langchain-ai/langchain/blob/b302691ff9ad841804e93e5addbdc53b6974473b/libs/core/langchain_core/callbacks/base.py#L23)