Called at the start of a Chat Model run, with the prompt(s) and the run ID.
handleChatModelStart(
llm: Serialized,
messages: BaseMessage<MessageStructure<MessageToolSet>, MessageType>[][],
runId: string,
parentRunId: string,
extraParams: Record<string, unknown>,
tags: string[],
metadata: Record<string, unknown>,
runName: string
): any