public function defaults($basePath = null)
    {
        $defaults = [];
        foreach ($this->_columns as $key => $value) {
            if ($basePath) {
                $fieldName = strpos($key, $basePath . '.') === 0 ? substr($key, strlen($basePath) + 1) : null;
            } else {
                $fieldName = $key;
            }
            if (!$fieldName || $fieldName === '*' || strpos($fieldName, '.') !== false) {
                continue;
            }
            if (isset($value['default'])) {
                $defaults[$fieldName] = $value['default'];
            }
        }
        return $defaults;
    }