public function getData()
    {
        $result = [];

        $hasValue = false;
        if ($this->data['from'] != $this::DEFAULT_VALUE) {
            $result['from'] = $this->data['from'];
            $hasValue = true;
        }

        if ($this->data['to'] != $this::DEFAULT_VALUE) {
            $result['to'] = $this->data['to'];
            $hasValue = true;
        }

        $isNullOperator = (isset($this->data['operator']) && ($this->data['operator'] === self::OPERATOR_ISNULL || $this->data['operator'] === self::OPERATOR_ISNOTNULL));
        if ($hasValue || $isNullOperator) {
            $result['operator'] = $this->data['operator'];
        }

        return $result;
    }