How to get the term id inside the start lvl method of category walker?

I'm trying to implement the category walker with wp_list_categories to help me manipulate list classes, which i want to get the term id within the start_lvl method, so i tried to use $category-term_id but errors thrown. now i just want to get the term id inside the start_lvl method to match the one i used inside the start_el output, please check this line in the following class

$output .= "span id=\"$category-term_id\" class=\"toggle\" onClick=\"toggleMe(this.id);\" style=\"cursor:pointer\"#9660/span";

I just copied the Walker_Category class and edited it to be like this:

            ?php
        //error_reporting(E_ALL);
        /*
        Plugin Name: YB Walker Categories List
        Plugin URI: https://prosentra.com
        Description: Displays a list of categories using  walker class
        Version: 1.0.0
        Author: Mohammad Omar
        Author URI: https://prosentra.com
        Text Domain: yb-walker-categories-list
        License: GPL2
        */

        if ( ! class_exists( 'YB_Cats_Walk' ) ) {
            class YB_Cats_Walk extends Walker_Category{
        public $tree_type = 'genre';
                /**
                 * Start Level.
                 *
                 * @see Walker::start_lvl()
                 * @since 3.0.0
                 *
                 * @access public
                 * @param mixed $output Passed by reference. Used to append additional content.
                 * @param int   $depth (default: 0) Depth of page. Used for padding.
                 * @param array $args (default: array()) Arguments.
                 * @return void
                 */

                public function start_lvl( $output, $depth = 0, $args = array() ) {
                    $indent = str_repeat( "\t", $depth );
                    $output .= "\n$indentul id = \"dropdown-$category-term_id\" style=\"display: none;\"\n";
                }

                public function end_lvl( $output, $depth = 0, $args = array() ) {
                    $indent = str_repeat("\t", $depth);
                    $output .= "$indent/ul\n";
                }

                public function start_el(  $output, $category, $depth = 0, $args = array(), $id = 0 ) {
                            /** This filter is documented in wp-includes/category-template.php */
                $cat_name = apply_filters(
                    'list_cats',
                    esc_attr( $category-name ),
                    $category
                );

                // Don't generate an element if the category name is empty.
                if ( ! $cat_name ) {
                    return;
                }

                $link = 'a href="' . esc_url( get_term_link( $category ) ) . '" ';
                if ( $args['use_desc_for_title']  ! empty( $category-description ) ) {
                    /**
                     * Filters the category description for display.
                     *
                     * @since 1.2.0
                     *
                     * @param string $description Category description.
                     * @param object $category    Category object.
                     */
                    $link .= 'title="' . esc_attr( strip_tags( apply_filters( 'category_description', $category-description, $category ) ) ) . '"';
                }

                $link .= '';
                $link .= $cat_name . '/a';

                if ( ! empty( $args['feed_image'] ) || ! empty( $args['feed'] ) ) {
                    $link .= ' ';

                    if ( empty( $args['feed_image'] ) ) {
                        $link .= '(';
                    }

                    $link .= 'a href="' . esc_url( get_term_feed_link( $category-term_id, $category-taxonomy, $args['feed_type'] ) ) . '"';

                    if ( empty( $args['feed'] ) ) {
                        $alt = ' alt="' . sprintf(__( 'Feed for all posts filed under %s' ), $cat_name ) . '"';
                    } else {
                        $alt = ' alt="' . $args['feed'] . '"';
                        $name = $args['feed'];
                        $link .= empty( $args['title'] ) ? '' : $args['title'];
                    }

                    $link .= '';

                    if ( empty( $args['feed_image'] ) ) {
                        $link .= $name;
                    } else {
                        $link .= "img src='" . $args['feed_image'] . "'$alt" . ' /';
                    }
                    $link .= '/a';

                    if ( empty( $args['feed_image'] ) ) {
                        $link .= ')';
                    }
                }

                if ( ! empty( $args['show_count'] ) ) {
                    $link .= ' (' . number_format_i18n( $category-count ) . ')';
                }
                if ( 'list' == $args['style'] ) {
                    $output .= "\tli";
                    if($this-has_children){

                        $css_classes = array(
                        'has-children',
                        'cat-item',
                        'cat-item-' . $category-term_id, 
                    );
                    }
                    $css_classes = array(
                    'has-children',
                        'cat-item',
                        'cat-item-' . $category-term_id,  
                    );


                    if ( ! empty( $args['current_category'] ) ) {
                        // 'current_category' can be an array, so we use `get_terms()`.
                        $_current_terms = get_terms( $category-taxonomy, array(
                            'include' = $args['current_category'],
                            'hide_empty' = false,
                        ) );

                        foreach ( $_current_terms as $_current_term ) {
                            if ( $category-term_id == $_current_term-term_id ) {
                                $css_classes[] = 'current-cat';
                            } elseif ( $category-term_id == $_current_term-parent ) {
                                $css_classes[] = 'current-cat-parent';
                            }
                            while ( $_current_term-parent ) {
                                if ( $category-term_id == $_current_term-parent ) {
                                    $css_classes[] =  'current-cat-ancestor';
                                    break;
                                }
                                $_current_term = get_term( $_current_term-parent, $category-taxonomy );
                            }
                        }
                    }

                    /**
                     * Filters the list of CSS classes to include with each category in the list.
                     *
                     * @since 4.2.0
                     *
                     * @see wp_list_categories()
                     *
                     * @param array  $css_classes An array of CSS classes to be applied to each list item.
                     * @param object $category    Category data object.
                     * @param int    $depth       Depth of page, used for padding.
                     * @param array  $args        An array of wp_list_categories() arguments.
                     */
                    $css_classes = implode( ' ', apply_filters( 'category_css_class', $css_classes, $category, $depth, $args ) );

                    $output .=  ' class="' . $css_classes . '"';
                    $output .= "$link\n";
                    if($this-has_children){
                    $output .= "span id=\"$category-term_id\" class=\"toggle\" onClick=\"toggleMe(this.id);\" style=\"cursor:pointer\"#9660/span";
                 }
                } elseif ( isset( $args['separator'] ) ) {
                    $output .= "\t$link" . $args['separator'] . "\n";
                } else {
                    $output .= "\t$linkbr /\n";
                }

                }
                public function end_el( $output, $page, $depth = 0, $args = array() ) {

                        $output .= "/li\n";
                }

                }

            }