code: def predict_y(self, model, pos):
          
          if model_para_num[model] == 2:
              y = all_models[model](pos, model_para[model][0], model_para[model][1])
          elif model_para_num[model] == 3:
              y = all_models[model](pos, model_para[model][0], model_para[model][1], model_para[model][2])
          elif model_para_num[model] == 4:
              y = all_models[model](pos, model_para[model][0], model_para[model][1], model_para[model][2], model_para[model][3])
          return y
docs: return the predict y of 'model' when epoch = pos
          
          Parameters
          ----------
          model: string
              name of the curve function model
          pos: int
              the epoch number of the position you want to predict
  
          Returns
          -------
          int:
              The expected matrix at pos