protected function validateAttributeCondition($attribute, $condition)
    {
        $attributeTypes = $this->getSearchAttributeTypes();
        if (!isset($attributeTypes[$attribute])) {
            $this->addError($this->filterAttributeName, $this->parseErrorMessage('unknownAttribute', ['attribute' => $attribute]));
            return;
        }

        if (is_array($condition)) {
            $operatorCount = 0;
            foreach ($condition as $rawOperator => $value) {
                if (isset($this->filterControls[$rawOperator])) {
                    $operator = $this->filterControls[$rawOperator];
                    if (isset($this->operatorTypes[$operator])) {
                        $operatorCount++;
                        $this->validateOperatorCondition($rawOperator, $value, $attribute);
                    }
                }
            }

            if ($operatorCount > 0) {
                if ($operatorCount < count($condition)) {
                    $this->addError($this->filterAttributeName, $this->parseErrorMessage('invalidAttributeValueFormat', ['attribute' => $attribute]));
                }
            } else {
                // attribute may allow array value:
                $this->validateAttributeValue($attribute, $condition);
            }
        } else {
            $this->validateAttributeValue($attribute, $condition);
        }
    }