feat(llm-observability): LangChain spans (#176)

* feat: refactor to dataclasses

* feat: spans

* test: fix part 1

* test: fix part 2

* test: fix part 3

* test: fix part n

* test: add langgraph agent test

* chore: bump and linters

* chore: bump

* fix: correctly capture a parent id when a custom trace_id is set

* test: multiple spans parent_ids

* fix: exception serialization

* refactor: ai_trace_name -> ai_span_name and ai_generation_id -> ai_span_id

* fix: logs typos

* Add minor breaking change note to changelog

* fix: naming

---------

Co-authored-by: Michael Matloka <[email protected]>

Author: skoob13

CHANGELOG.md

@@ -1,11 +1,18 @@
-## 3.11.0 - 2025-01-27
+## 3.11.0 - 2025-01-28
 
-1. Fix serialiazation of Pydantic models in methods.
+1. Add the `$ai_span` event to the LangChain callback handler to capture the input and output of intermediary chains.
+   > LLM observability naming change: event property `$ai_trace_name` is now `$ai_span_name`.
+
+2. Fix serialiazation of Pydantic models in methods.
 
 ## 3.10.0 - 2025-01-24
 
 1. Add `$ai_error` and `$ai_is_error` properties to LangChain callback handler, OpenAI, and Anthropic.
 
+## 3.9.3 - 2025-01-23
+
+1. Fix capturing of multiple traces in the LangChain callback handler.
+
 ## 3.9.2 - 2025-01-22
 
 1. Fix importing of LangChain callback handler under certain circumstances.