code: def transaction(self, tx_hash):
          
          endpoint = '/transactions/{tx_hash}'.format(tx_hash=tx_hash)
          return self.query(endpoint)
docs: The transaction details endpoint provides information on a single
          transaction.
  
          `GET /transactions/{hash}
          <https://www.stellar.org/developers/horizon/reference/endpoints/transactions-single.html>`_
  
          :param str tx_hash: The hex-encoded transaction hash.
          :return: A single transaction's details.
          :rtype: dict