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<?php     //<~ don't add me in

add_filter( 'wp_nav_menu_items', 'my_account_loginout_link', 10, 2 );
/**
 * Add WooCommerce My Account Login/Logout to Menu
 * 
 * @see https://support.woothemes.com/hc/en-us/articles/203106357-Add-Login-Logout-Links-To-The-Custom-Primary-Menu-Area
 */
function my_account_loginout_link( $items, $args ) {
    if (is_user_logged_in() && $args->theme_location == 'primary') { //change your theme location menu to suit
        $items .= '<li><a href="'. wp_logout_url( get_permalink( wc_get_page_id( 'shop' ) ) ) .'">Log Out</a></li>'; //change logout link, here it goes to 'shop', you may want to put it to 'myaccount'
    }
    elseif (!is_user_logged_in() && $args->theme_location == 'primary') {//change your theme location menu to suit
        $items .= '<li><a href="' . get_permalink( wc_get_page_id( 'myaccount' ) ) . '">Log In</a></li>';
    }
    return $items;
}