fix ruff and added changelog

Author: wrisa

instrumentation-genai/opentelemetry-instrumentation-langchain/CHANGELOG.md

@@ -7,5 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fixed typecheck.
+  ([#3773](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3773))
+- 
 - Added span support for genAI langchain llm invocation.
   ([#3665](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3665))

instrumentation-genai/opentelemetry-instrumentation-langchain/src/opentelemetry/instrumentation/langchain/span_manager.py

@@ -31,7 +31,7 @@
 @dataclass
 class _SpanState:
     span: Span
-    children: List[UUID] = field(default_factory=list) # type: ignore [reportUnknownVariableType]
+    children: List[UUID] = field(default_factory=list)  # type: ignore [reportUnknownVariableType]
 
 
 class _SpanManager: