Proposal for Mutual Reference Implementation between _arun and _run Methods in langchain

[klae01]

Hello, langchain community members,

Recently, while exploring the implementation of asynchronous tools, I discovered challenges in certain scenarios where tools could either be exclusively implemented asynchronously or synchronously. As a result, I'd like to propose a solution that strengthens the connection between asynchronous and synchronous functions and reduces redundant implementation.

I've demonstrated through the async_tool_runner.py script how _arun can be made operational in various situations using _run. The central idea I wish to convey with this script is to enable synchronous execution through _run when it hasn't been implemented.

Here's my proposed method of implementation:

1. By default in langchain, the _run method refers to and executes _arun.
2. If _arun is not implemented, it references and executes the _run method.
3. An error is triggered if _arun and _run end up in a mutual reference state.

Through this implementation, developers can fulfill both scenarios by implementing either _arun or _run. Of course, implementing both would be ideal, but there might be circumstances where only one method can be implemented.

I'd love to hear your thoughts on this proposal. If you have additional ideas or feedback related to this, please share.

Thank you.