Walker Class - Mega Menu

<?php

class Shape_Nav_Menu_Walker extends Walker_Nav_Menu {
    function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0) {
        global $wp_query;
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';

        global $wp_query;

        $class_names = $value = '';

        $classes = empty( $item->classes ) ? array() : (array) $item->classes;

        // if its the mega menu
        if( $item->object == 'mega_menu' ) {
            $classes[] = 'mega-par';
        }

        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
        $class_names = ' class="' . esc_attr( $class_names ) . '"';

        $output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';

        $attributes = ! empty( $item->attr_title ) ? ' title="' . esc_attr( $item->attr_title ) .'"' : '';
        $attributes .= ! empty( $item->target ) ? ' target="' . esc_attr( $item->target ) .'"' : '';
        $attributes .= ! empty( $item->xfn ) ? ' rel="' . esc_attr( $item->xfn ) .'"' : '';
        $attributes .= ! empty( $item->url ) ? ' href="' . esc_attr( $item->url ) .'"' : '';

        $item_output = $args->before;
        $item_output .= '<a'. $attributes .'>';
        $item_output .= $args->link_before . do_shortcode(  apply_filters( 'the_title', $item->title, $item->ID )) . $args->link_after;
        $item_output .= '<span class="sub">' . do_shortcode( $item->description ) . '</span>';
        $item_output .= '</a>';
        $item_output .= $args->after;

        if( $item->object == 'mega_menu' ) {

            $getPost = get_post($item->object_id);
            $item_output .= '<ul class="shape-mega-menu custom_mega_menu">'. do_shortcode( $getPost->post_content    ) .'</ul>';

            $shortcodes_custom_css = get_post_meta( $getPost->ID, '_wpb_shortcodes_custom_css', true );
            if ( ! empty( $shortcodes_custom_css ) ) {
                echo '<style type="text/css" data-type="vc_shortcodes-custom-css">';
                echo $shortcodes_custom_css;
                echo '</style>';
            }

            $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
        } else {
            $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
        }

    }
}