async def get_txn(self, txn: int) -> str:
LOGGER.debug('<STR_LIT>', txn)<EOL>rv_json = json.dumps({})<EOL>req_json = await ledger.build_get_txn_request(self.did, None, txn)<EOL>resp = json.loads(await self._submit(req_json))<EOL>rv_json = json.dumps((resp['<STR_LIT:result>'].get('<STR_LIT:data>', {}) or {}).get('<STR_LIT>', {}))  <EOL>LOGGER.debug('<STR_LIT>', rv_json)<EOL>return rv_json<EOL>
Find a transaction on the distributed ledger by its sequence number.

:param txn: transaction number
:return: json sequence number of transaction, null for no match