code: func HasGetSetVarFunc(expr Expression) bool {
  	scalaFunc, ok := expr.(*ScalarFunction)
  	if !ok {
  		return false
  	}
  	if scalaFunc.FuncName.L == ast.SetVar {
  		return true
  	}
  	if scalaFunc.FuncName.L == ast.GetVar {
  		return true
  	}
  	for _, arg := range scalaFunc.GetArgs() {
  		if HasGetSetVarFunc(arg) {
  			return true
  		}
  	}
  	return false
  }
docs: // HasGetSetVarFunc checks whether an expression contains SetVar/GetVar function.