public static function standard_fields($with_attr = true)
 {
     $fields = array('image' => __('Image', 'yith-woocommerce-compare'), 'title' => __('Title', 'yith-woocommerce-compare'), 'price' => __('Price', 'yith-woocommerce-compare'), 'add-to-cart' => __('Add to cart', 'yith-woocommerce-compare'), 'description' => __('Description', 'yith-woocommerce-compare'), 'stock' => __('Availability', 'yith-woocommerce-compare'));
     if ($with_attr) {
         $fields = array_merge($fields, YITH_Woocompare_Helper::attribute_taxonomies());
     }
     return $fields;
 }
        /**
         * Create new Woocommerce admin field: checkboxes
         *
         * @access public
         * @param array $value
         * @return void
         * @since 1.0.0
         */
        public function admin_fields_attributes($value)
        {
            $fields = array_merge($this->default_fields, YITH_Woocompare_Helper::attribute_taxonomies());
            $all = array();
            foreach (array_keys($fields) as $field) {
                $all[$field] = true;
            }
            $checkboxes = get_option($value['id'], $value['default'] == 'all' ? $all : array());
            // add fields that are not still saved
            $checkboxes = wp_parse_args($checkboxes, $all);
            //$checkboxes = array_merge( $checkboxes, array_diff_assoc( $checkboxes, $all ) );
            ?>
        <tr valign="top">
            <th scope="row" class="titledesc">
                <label for="<?php 
            echo esc_attr($value['id']);
            ?>
"><?php 
            echo $value['name'];
            ?>
</label>
            </th>

            <td class="forminp attributes">
                <p class="description"><?php 
            echo $value['desc'];
            ?>
</p>
                <ul class="fields">
                    <?php 
            foreach ($checkboxes as $slug => $checked) {
                ?>
                    <li><label><input type="checkbox" name="<?php 
                echo $value['id'];
                ?>
[]" id="<?php 
                echo $value['id'];
                ?>
_<?php 
                echo $slug;
                ?>
" value="<?php 
                echo $slug;
                ?>
"<?php 
                checked($checked);
                ?>
 /> <?php 
                echo $fields[$slug];
                ?>
</label></li><?php 
            }
            ?>
                </ul>
                <input type="hidden" name="<?php 
            echo $value['id'];
            ?>
_positions" value="<?php 
            echo implode(',', array_keys($checkboxes));
            ?>
" />
            </td>
        </tr>
    <?php 
        }