Helper/Order.php
private function addCustomerDetails($quote, $email)
    {
        $quote->setCustomerEmail($email);
        if (!$quote->getCustomerId()) {
            $quote->setCustomerId(null);
            $quote->setCheckoutMethod('guest');
            $quote->setCustomerIsGuest(true);
            $quote->setCustomerGroupId(GroupInterface::NOT_LOGGED_IN_ID);
        }
    }
private function addCustomerDetails($quote, $email)
    {
        $quote->setCustomerEmail($email);
        if (!$quote->getCustomerId()) {
            $quote->setCustomerId(null);
            $quote->setCheckoutMethod('guest');
            $quote->setCustomerIsGuest(true);
            $quote->setCustomerGroupId(GroupInterface::NOT_LOGGED_IN_ID);
        }
    }
private function addCustomerDetails ( $ quote , $ email ) { $ quote -> setCustomerEmail ( $ email ) ; if ( ! $ quote -> getCustomerId ( ) ) { $ quote -> setCustomerId ( null ) ; $ quote -> setCheckoutMethod ( 'guest' ) ; $ quote -> setCustomerIsGuest ( true ) ; $ quote -> setCustomerGroupId ( GroupInterface :: NOT_LOGGED_IN_ID ) ; } }
Set quote customer email and guest checkout parameters

@param Quote $quote
@param string $email

@return void
Set quote customer email and guest checkout parameters