/** Blocks until the activity is terminated, or until the timeout is elapsed
* Raises: timeout exception.*/
virtual Activity* wait_for(double timeout) = 0;
/** Blocks until the activity is terminated, or until the timeout is elapsed
* Raises: timeout exception.*/
virtual Activity* wait_for(double timeout) = 0;
/** Cancel that activity */
virtual Activity* cancel() = 0;
/** Retrieve the current state of the activity */
/** Cancel that activity */
virtual Activity* cancel() = 0;
/** Retrieve the current state of the activity */