How To make custom variables for the Automate woo

functions.php

<?php
add_filter( 'automatewoo/variables', 'automatewoo_custom_variable' );
function automatewoo_custom_variable( $variables ) {
    /**
     * Add Path of the file create folder in the theme file and see below file location.
     */
    $variables['order']['veriable_name'] = require_once get_theme_file_path().'/automatewoo/includes/variables/order-variable-name.php';
    return $variables;
}

order-variable-name.php

<?php


class AutomateWooPayfastTokenVariable extends AutomateWoo\Variable {

    protected $name = 'order.custom_variable';

    public $use_fallback = false;

    function load_admin_details() {
        $this->description = __( 'Genenrate a custom variable', 'automatewoo');
        parent::load_admin_details();
    }

    /**
     * @param $order WC_Order
     * @param $parameters array
     * @return string|false
     */
    public function get_value( $order, $parameters ) {
        $custom_meta_value = get_post_meta($order->get_id(), '_custom_meta_key', true);
        if ( empty( $custom_meta_value ) ) {
            return false;
        }

        return $custom_meta_value;

    }

}
return new AutomateWooPayfastTokenVariable();