code: def pop_task(self, number):
          
          if not self._started.isSet():
              if number is True:
                  self._tasks = []
                  self._tasks_tracked = {}
              elif number > 0:
                  last_task_id = len(self._tasks) - 1
                  for i in xrange(number):
                      self._tasks.pop()
                      self._tasks_tracked.pop(last_task_id - i, None)
          else:
              log.error('%s cannot delete tasks (is started).' % self)
              raise RuntimeError('%s cannot delete tasks (is started).' % self)
docs: Removes a previously added **task** from the ``NuMap`` instance.
          
          Arguments:
          
            - number (``int`` or ``True``) A positive integer specifying the 
              number of **tasks** to pop. If  number is set ``True`` all **tasks**
              will be popped.