code: def demo():
      
      from time import sleep
      maxProgress = 1000
      with ProgressBar(max=maxProgress) as progressbar:
          for i in range(-100, maxProgress):
              sleep(0.01)
              progressbar.update(i)
      progressbar2 = ProgressBar(max=maxProgress)
      for s in progressbar2.iterate(range(maxProgress)):
          sleep(0.01)
      for s in progressbar2.iterate(range(maxProgress), format='iteration %d'):
          sleep(0.01)
docs: Demonstrate progress bar.