def execute(self):
        """Run all child tasks, in order, waiting for completion of each.
        Return the result of the final child task's execution.
        """
        while self.index < len(self.tasklist):
            res = self.step()
            self.logger.debug('SeqSet task %i has completed with result %s' %
                              (self.index, res))

        # Returns result of last task to quit
        return res
Run all child tasks, in order, waiting for completion of each.
        Return the result of the final child task's execution.