langgraph 0.2.2

Summary of Changes

• Improved error handling in StateGraph's reducer function validation, providing clearer error messages when invalid reducer signatures are detected #1261
• Enhanced the output update mapping in Pregel I/O with better handling of empty updates and simplified logic #1261

Detailed Changes

langgraph.graph.state.StateGraph

• Improved validation of reducer functions with clearer error messages when detecting invalid signatures #1261
• Now raises a specific ValueError with helpful message "Invalid reducer signature. Expected (a, b) -> c" when a reducer function has incorrect parameters

langgraph.pregel.io.map_output_updates

• Refactored implementation to simplify logic and improve readability #1261
• Added handling for empty update cases (setting to None when no values are present)
• Improved consistency in how grouped values are processed