code: def execute(self):
          
          self.count = 0
          self.taskset = []
          self.results = {}
          self.totaltime = time.time()
  
          # Register termination callbacks for all my child tasks.
          for task in list(self.taskseq):
              self.taskset.append(task)
              task.add_callback('resolved', self.child_done, self.count)
              self.count += 1
  
          self.numtasks = self.count
  
          # Now start each child task.
          with self.regcond:
              for task in list(self.taskset):
                  task.initialize(self)
  
                  task.start()
  
              # Account for time needed to start subtasks
              self.totaltime = time.time() - self.totaltime
  
              # Now give up the critical section and wait for last child
              # task to terminate.
              while self.count > 0:
                  self.regcond.wait()
  
          # Scan results for errors (exceptions) and raise the first one we find
          for key in self.results.keys():
              value = self.results[key]
              if isinstance(value, Exception):
                  (count, task) = key
                  self.logger.error("Child task %s terminated with exception: %s" % (
                      task.tag, str(value)))
                  raise value
  
          return 0
docs: Run all child tasks concurrently in separate threads.
          Return 0 after all child tasks have completed execution.