code: def set_display_mode(self, mytz, fmt="%Y-%m-%d %H:%M:%S %Z%z"):
          
          for item in self.comments:
              item.set_display_mode(mytz, fmt)
docs: Call set_display_mode on items in self.comments with given args.
  
          :arg mytz:      A pytz.timezone object.
  
          :arg fmt="%Y-%m-%d%H:%M:%S%Z%z":   Optional format string.
  
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          PURPOSE:        Call set_display_mode(mytz, fmt) for everything in
                          self.comments.