It looks like you've copied this method over verbatim from [gateway.rb](https://github.com/Shopify/active_merchant/blob/1e8658bc245e1524f4628fe80d76a19001ec1cdc/lib/active_merchant/billing/gateway.rb#L142-L160) in response to my [previous note](https://github.com/Shopify/active_merchant/pull/1027#discussion-diff-9874514) about making use of this method for handling amounts correctly.

Because this class inherits from ActiveMerchant::Billing::Gateway, this #amount method is already available in your class, so no need to copy and paste the entire method. It can be removed from here.