public function validateValidItem()
    {
        if (!$this->value) {
            return;
        }

        // load allowed values in values_list
        // @todo Imants: Actually we don't need to load all values from Model in
        //       array, just to check couple of posted values.
        //       Probably we should do SELECT * FROM t WHERE id IN ($values) or
        //       something like that to limit array size and time spent on
        //       parsing all DB records in Model.
        $this->getValueList();

        $values = explode($this->separator, $this->value);
        foreach ($values as $v) {
            if (!isset($this->value_list[$v])) {
                $this->displayFieldError("Value $v is not one of the offered values");

                return $this->validate();
            }
        }
    }