code: def get(self, txn_id):
          
          if txn_id not in self._receipt_db:
              raise KeyError('Unknown transaction id {}'.format(txn_id))
  
          txn_receipt_bytes = self._receipt_db[txn_id]
          txn_receipt = TransactionReceipt()
          txn_receipt.ParseFromString(txn_receipt_bytes)
          return txn_receipt
docs: Returns the TransactionReceipt
  
          Args:
              txn_id (str): the id of the transaction for which the receipt
                  should be retrieved.
  
          Returns:
              TransactionReceipt: The receipt for the given transaction id.
  
          Raises:
              KeyError: if the transaction id is unknown.