apply_filters( 'category_css_class', string[] $css_classes, WP_Term $category, int $depth, array $args )

239			 *240			 * @param string[] $css_classes An array of CSS classes to be applied to each list item.241			 * @param WP_Term  $category    Category data object.242			 * @param int      $depth       Depth of page, used for padding.243			 * @param array    $args        An array of wp_list_categories() arguments.244			 */245			$css_classes = implode( ' ', apply_filters( 'category_css_class', $css_classes, $category, $depth, $args ) );246			$css_classes = $css_classes ? ' class="' . esc_attr( $css_classes ) . '"' : '';247 248			$output .= $css_classes;249			$output .= ">$link\n";250		} elseif ( isset( $args['separator'] ) ) {251			$output .= "\t$link" . $args['separator'] . "\n";