LangChain Expression Language

LangChain has introduced a new syntax, called LangChain Expression Language (LCEL), for creating chains with composition. This comes along with a new interface that supports batch, async, and streaming out of the box. LCEL is aimed at making it easier to construct complex chains and pairs nicely with LangSmith - the platform recently released aimed at making it easier to go from prototype to production. The syntax allows for multiple LLM calls, input construction for LLMs, and using the output of LLMs in various applications.