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title: prefactor_langchain.metadata_extractor module
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# prefactor_langchain.metadata_extractor module

Utilities for extracting metadata from LangChain objects.

### prefactor_langchain.metadata_extractor.extract_error_info(error: Exception) → [ErrorInfo](prefactor_langchain.spans.md#prefactor_langchain.spans.ErrorInfo)

Extract error information from an exception.

* **Parameters:**
  **error** – The exception to extract information from.
* **Returns:**
  ErrorInfo containing error details.

### prefactor_langchain.metadata_extractor.extract_token_usage(response: Any) → [TokenUsage](prefactor_langchain.spans.md#prefactor_langchain.spans.TokenUsage) | None

Extract token usage from a ModelResponse.

Checks each message in `response.result` for `usage_metadata`
(the standard LangChain field populated by all providers), accumulating
totals across messages.

* **Parameters:**
  **response** – A ModelResponse object from LangChain.
* **Returns:**
  TokenUsage if available, None otherwise.