code: def transform_txn_for_ledger(txn):
          
          if get_type(txn) == ATTRIB:
              txn = DomainReqHandler.transform_attrib_for_ledger(txn)
          return txn
docs: Some transactions need to be transformed before they can be stored in the
          ledger, eg. storing certain payload in another data store and only its
          hash in the ledger