<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def start_tasks(self):
 """ Start however many tasks we can based on our limits and what we have left to finish. """

        while self.tasks_at_once > len(self.pending_results) and self._has_more_tasks():
            task, parent_result = self.tasks.popleft()
            self.execute_task(task, parent_result)