https://medium.com/@elliotchance/implementing-repeatable-read-and-serializable-transaction-isolation-8b806a14026e

8.py

class TransactionTest:
    def __init__(self, transaction_type):
        self.table = Table()
        client = self.table.new_transaction(ReadCommittedTransaction)
        client.add_record(id=1, name="Joe")
        client.add_record(id=3, name="Jill")
        client.commit()
        self.client1 = self.table.new_transaction(transaction_type)
        self.client2 = self.table.new_transaction(transaction_type)
        
    def run_test(self):
        try:
            return self.run()
        except RollbackException:
            return False
          
    def result(self):
        if self.run_test():
            return u'✔'
          
        return u'✘'