It's just out of date, I no longer need an answer to it.

Using @Eduard Lebedyuk  suggestion, I implemented it like this

Method BillingDocumentRequestRequestIn(pRequest As ARInvoices.Request.BillingDocumentRequestRequestInRequest, Output pResponse As ARInvoices.Response.BillingDocumentRequestRequestInResponse) As %Library.Status
{
  Set tSC = ..Adapter.InvokeMethod("BillingDocumentRequestRequestIn",,pRequest.MessageHeader,pRequest.GlobalParameters,pRequest.ActionControl,pRequest.BillableDocument)  Quit:$$$ISERR(tSC) tSC
  Set tSC = pRequest.NewResponse(.pResponse)  Quit:$$$ISERR(tSC) tSC
  Set StatusCode = ..Adapter.%Client.HttpResponse.StatusCode
  $$$TRACE(StatusCode)
  Quit $$$OK
}