code: def generate_parameters(self, parameter_id):
          
          if len(self.population) <= 0:
              logger.debug("the len of poplution lower than zero.")
              raise Exception('The population is empty')
          pos = -1
          for i in range(len(self.population)):
              if self.population[i].result == None:
                  pos = i
                  break
          if pos != -1:
              indiv = copy.deepcopy(self.population[pos])
              self.population.pop(pos)
              temp = json.loads(graph_dumps(indiv.config))
          else:
              random.shuffle(self.population)
              if self.population[0].result < self.population[1].result:
                  self.population[0] = self.population[1]
              indiv = copy.deepcopy(self.population[0])
              self.population.pop(1)
              indiv.mutation()
              graph = indiv.config
              temp =  json.loads(graph_dumps(graph))
          logger.debug('generate_parameter return value is:')
          logger.debug(temp)
          return temp
docs: Returns a set of trial graph config, as a serializable object.
          parameter_id : int