Implement new "Event.parents" property

[zchn]

What problem or use case are you trying to solve?
In the EventStream, subscribers process any new Event objects and emit new Event objects according.

Currently, Event objects in an EventStream contain no information about what parent Event objects this Event is a result of, making it hard to figure out the provenance information about an Event.

We want to add a parents property to the Event object (class definition in openhands/events/event.py) to carry such provenance information.

Do you have thoughts on the technical implementation?

1. In the Event class in openhands/events/event.py, a new parents property should be added, and it should be a list of ParentEvent objects with two properties: id: int and method: str. The id property records the id of the parent event, and the method property records what kind of processing was done to derive the new event from the parent event.
2. Whenever a new event is created (typically when EventStream.add_event is called), it should add parent information to the newly created event, based on the existing event received and being processed.

Additional context

1. Implement appropriate tests.
2. Make sure to run applicable unit tests and lint tests to make sure they all pass.

[zchn]

OpenHands started fixing the issue! You can monitor the progress here.

[zchn]

OpenHands started fixing the issue! You can monitor the progress here.