How do i add the document_type_code to a mustangproject invoice.

my try:

Invoice invoice = new Invoice().setReferenceNumber(invoiceData.invoiceNumber.getContent())
                    .setNumber(invoiceData.invoiceNumber.getContent())
                    .setDocumentCode("388")

result:

<rsm:ExchangedDocument>
    <ram:ID>INV123456</ram:ID>
    <ram:TypeCode>381</ram:TypeCode>
    <ram:IssueDateTime>
      <udt:DateTimeString format="102">20240527</udt:DateTimeString>
    </ram:IssueDateTime>
  </rsm:ExchangedDocument>

I searched in the official repo.
is there eventually even a list that does a map between xrechnung functions (and the BT’s) and the Mustangproject-functions? would be super helpful. Thanks