public function columnFieldsMetaBoxContent($post, $args)
    {
        $fields = $args['args'][0];
        $fieldValues = get_post_meta($post->ID, 'modularity-mod-posts-expandable-list', true);

        foreach ($fields as $field) {
            $fieldSlug = sanitize_title($field);
            $value = isset($fieldValues[$fieldSlug]) && !empty($fieldValues[$fieldSlug]) ? $fieldValues[$fieldSlug] : '';
            echo '
                <p>
                    <label for="mod-' . $fieldSlug . '">' . $field . ':</label>
                    <input value="' . $value . '" class="widefat" type="text" name="modularity-mod-posts-expandable-list[' . sanitize_title($field) . ']" id="mod-' . sanitize_title($field) . '">
                </p>
            ';
        }

        echo wp_nonce_field('save_columns', 'modularity_post_columns');
    }