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

9.py

class DirtyRead(TransactionTest):
    def run(self):
        result1 = self.client1.fetch_record(id=1)
        self.client2.update_record(id=1, name="Joe 2")
        result2 = self.client1.fetch_record(id=1)
        return result1 != result2
      
class NonRepeatableRead(TransactionTest):
    def run(self):
        result1 = self.client1.fetch_record(id=1)
        self.client2.update_record(id=1, name="Joe 2")
        self.client2.commit()
        result2 = self.client1.fetch_record(id=1)
        
        return result1 != result2
      
class PhantomRead(TransactionTest):
    def run(self):
        result1 = len(self.client1.fetch(lambda r: 1 <= r['id'] <= 3))
        self.client2.add_record(id=2, name="John")
        self.client2.commit()
        result2 = self.client1.count_records(min_id=1, max_id=3)
        
        return result1 != result2