code: def calculate_progress(self, scan_id):
          
  
          t_prog = dict()
          for target in self.get_scan_target(scan_id):
              t_prog[target] = self.get_scan_target_progress(scan_id, target)
          return sum(t_prog.values())/len(t_prog)
docs: Calculate the total scan progress from the
          partial target progress.