Script below is throwing up an error "JS_ Exception - TypeError log.debug is not a function"

I basically want to set the price level to 'custom' whenever a user enters a line on a sales order.

Help appreciated. Thank you.

/**
 * @NApiVersion 2.1
 * @NScriptType ClientScript
 * @NModuleScope SameAccount
 */

define(['N/search', 'N/log'], (search, log) => {
    function fieldChanged(scriptContext) {
        const sublistVal = scriptContext.sublistId;
        if (sublistVal === 'item') {
            try {
                rec.setCurrentSublistValue({
                    sublistId: sublistVal,
                    fieldId: 'price_value',
                    value: 'custom',
                    ignoreFieldChange: true
                });
            } catch(e) {
                log.debug({
                    title: 'Error',
                    details: 'Unable to set price level'
                });
            }
        }
    }
    return {
        fieldChanged: fieldChanged
    };
});