StreamEvent

Event names are of the format: on_[runnable_type]_(start|stream|end).

Runnable types are one of:

• llm - used by non chat models
• chat_model - used by chat models
• prompt -- e.g., ChatPromptTemplate
• tool -- LangChain tools
• chain - most Runnables are of this type

Further, the events are categorized as one of:

• start - when the runnable starts
• stream - when the runnable is streaming
• end - when the runnable ends

start, stream and end are associated with slightly different data payload.

Please see the documentation for EventData for more details.

An randomly generated ID to keep track of the execution of the given runnable.

Each child runnable that gets invoked as part of the execution of a parent runnable is assigned its own unique ID.