Revise Task interface about clay HOT 3 CLOSED

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1. finished_computatation is a question, computation_finished information. Do you have better ideas for names?
2. Maybe get_next_subtask?
3. In current tasks there is no difference. We can imagine some scenarios where it may be a difference, but in most cases it should mean the same.

from clay.

1. maybe on_computation_finished, since this is kind of a callback? Or react_to_computation_finished. Some general convention would be useful here.
2. sounds good
3. I see

from clay.

1. Personally I prefer react_to_computation_finished (convention with verb), but other proposition is also good.

from clay.