从网上学习了大神分享的mplus有调节的中介效应命令

但是点击运行显示错误
错误语句提示如下：
*** ERROR in MODEL CONSTRAINT command
  A parameter label or the constant 0 must appear on the left-hand side of a MODEL CONSTRAINT
  statement.  A parameter label must be declared in the MODEL command or with the NEW or PLOT
  options in MODEL CONSTRAINT before it can be used.  Problem with:  DIR_LOW

请教各位大神，这是什么错误呀，要怎么解决呢（实在是没找到这方面的问题答案）
谢谢🙏祝各位大神学术之路节节高升！

大神的命令如下：
VARIABLE: NAMES ARE x m1 w v1 v2 v3 y;
! 给数据中变量命名
USEVARIABLES = X M1 v1 v2 v3  Y xm1;
DEFINE: Xm1 = X*m1;  
ANALYSIS:
          TYPE = GENERAL;
          ESTIMATOR = ML;
          BOOTSTRAP = 2000;
MODEL:
    m by v1 v2 v3;
    [Y] (b0);
    Y ON M (b1);
    Y ON X (cdash1);  
    Y ON m1 (cdash2);  
    Y ON Xm1 (cdash3);   
    [M] (a0);  
    M ON X (a1);  

MODEL CONSTRAINT:
  NEW(LOW_W MED_W HIGH_W a1b1 DIR_LO DIR_MED DIR_HI TOT_LO TOT_MED TOT_HI);  

  LOW_W = 2.6;
  MED_W = 4.7;  
  HIGH_W = 6.7;

  A1B1 = a1*b1;
  DIR_LOW =  cdash1 + cdash3*LOW_W;
  DIR_MED = cdash1 + cdash3*MED_W;
  DIR_HIGH =  cdash1 + cdash3*HIGH_W;

  TOT_LOW = DIR_LOW + A1B1;
  TOT_MED = DIR_MED + A1B1;
  TOT_HIGH = DIR_HIGH + A1B1;

  PLOT(LOMOD MEDMOD HIMOD);
  LOOP(XVAL,1,5,0.1);
  LOMOD = (b0 + a0*b1 + cdash2*LOW_W) + TOT_LOW*XVAL;
  MEDMOD = (b0 + a0*b1 + cdash2*MED_W) + TOT_MED*XVAL;
  HIMOD = (b0 + a0*b1 + cdash2*HIGH_W)+ TOT_HIGH*XVAL;

PLOT:
  TYPE = plot2;
OUTPUT:
  STAND CINT(bcbootstrap);