WP_CLI\Formatter::find_item_key PHP Method

    private function find_item_key($item, $field)
    {
        foreach (array($field, $this->prefix . '_' . $field) as $maybe_key) {
            if (is_object($item) && (property_exists($item, $maybe_key) || isset($item->{$maybe_key})) || is_array($item) && array_key_exists($maybe_key, $item)) {
                $key = $maybe_key;
                break;
            }
        }
        if (!isset($key)) {
            \WP_CLI::error("Invalid field: {$field}.");
        }
        return $key;
    }