code: public function end($taskName)
      {
          if (!isset($this->_tasks[$taskName])) {
              throw new Exception("Undefined task name: `'{$taskName}`.");
          }
          $task = $this->_tasks[$taskName];
          $task->end();
          return $task;
      }
docs: Ends the timer for a task
  
  @param  string $taskName The taskname to stop the timer for.
  @return object           The stopped task.