6 files declare their use of PaymentMethod in Ubercart 8.4

CreditController.php in payment/uc_credit/src/Controller/CreditController.php

Payment.php in payment/uc_payment/src/Plugin/Ubercart/OrderPane/Payment.php

PaymentMethodManager.php in payment/uc_payment/src/Plugin/PaymentMethodManager.php

PaymentMethodPane.php in payment/uc_payment/src/Plugin/Ubercart/CheckoutPane/PaymentMethodPane.php

uc_payment.module in payment/uc_payment/uc_payment.module

Defines the payment API that lets payment modules interact with Ubercart.

uc_payment.tokens.inc in payment/uc_payment/uc_payment.tokens.inc

Token hooks for the uc_payment module.