Task Lifecycle

Task states may be:

PENDING - the default, on the class
FINISHED - set in set_result and set_exception

When a Task's .cancel gets called, the state is still PENDING.

Task calls Future's set_result on the step it returns. This changes the state and schedules callbacks to run on the next loop iteration.

CANCELLED - only on Future, not on Tasks. When someone calls .cancel() on a Future.