Bad carrier account in single call example

[InfiniteCodeMonkeys]

I'm in test mode and am trying to work through the example found here: https://goshippo.com/docs/single-call/

It's giving me the following error:
{type: "ShippoAPIError", message: "The data you sent was not accepted as valid", detail: {…}, path: "/transactions/?shipment=&carrier_account=b741b99f9…9b54272834bc478c&servicelevel_token=usps_priority", statusCode: 400}
detail:
carrier_account: ["Account with object_id b741b99f95e841639b54272834bc478c was not found."]
proto: Object
message: "The data you sent was not accepted as valid"
path: "/transactions/?shipment=&carrier_account=b741b99f95e841639b54272834bc478c&servicelevel_token=usps_priority"
statusCode: 400
type: "ShippoAPIError"
proto: Object

Am I meant to swap out the carrier account ID with one of my own?