How does `task_key` is updated? How is `task_key` determined for new task?

[jeeyung]

I checked the code in textbox/model/ptg.py.
However, I am confused that how task_key is updated.
Is the only last embedding updated?

Also, I am wondering how to determine task_key for new task..
Doesn't it refer to the other tasks?

[jeeyung]

I realized that you assume that source_prompts are given. My mistake.
Thanks!