This is not sweet potato; what is it?
Last year I rooted the Asian sweet potato vine (for eatting its leaves but not tuber) from its stem and planted it in my vege bed. When this volunteer seedling came up early in April, I thought that it was for some reason coming from the sweet potato I planted last year growing a tuber or something. The young leaves looked like sweet potato's. Then, I was out of town for 2 weeks and came back home. This seedling grows not like sweet potato any more.
I suspect that it is growing from some of my compost. I have to admit that I don't follow the rule for using the compost pile. I did not separate the "composted" from the new compost materials, so I probably picked up un-composted fruit seeds from the compost pile.
What is it? Please ID. Thank you.