mbchang

Modifying `StdoutCallbackHandler` could work, but I wonder if it could cause difficulties in separating functionality, which was why I thought that using an explicitly separate handler could make things clearer...

UPDATE: I realized that one solution to the above concerns could be for the user to pass in two `StdoutCallBackHandlers`, one with a file and one without a file, to...

On second thought, passing in two `StdoutCallBackHandlers` might not work. This is because when the callbacks are configured, if `verbose=True`, then [this line](https://github.com/hwchase17/langchain/blob/f75f0dbad6030012470a275bf00f84506cd3469f/langchain/callbacks/manager.py#L857) checks instantiates a new `StdoutCallBackHandler` to log...

Oops, apologies. It should be fixed now. We should expect four files to have changed.

Yes good point. I was originally thinking about pushing this pull request to establish the parallel abstraction to start, and then adding the asynchronous feature in a follow-up pull request...

I have just updated the code to allow for concurrent execution. It is also possible to nest `ParallelChain`s inside other `ParallelChain`s, all executing concurrently, such as the following ``` num_child_chains...

Hey @agola11, thanks for the comments, and thanks for introducing the async api to the LangChain library. I have rewritten the multithreading code to only use the same `asyncio` functions...