SupportsPreCommitTopology (Flink : Runtime 2.0-preview1 API)

```
@Experimental
public interface SupportsPreCommitTopology<WriterResultT,CommittableT>
```
Allows expert users to implement a custom topology after SinkWriter and before Committer.
It is recommended to use immutable committables because mutating committables can have unexpected side-effects.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`DataStream<CommittableMessage<CommittableT>>`	`addPreCommitTopology(DataStream<CommittableMessage<WriterResultT>> committables)`	Intercepts and modifies the committables sent on checkpoint or at end of input.
`org.apache.flink.core.io.SimpleVersionedSerializer<WriterResultT>`	`getWriteResultSerializer()`	Returns the serializer of the WriteResult type.

- Method Detail
  - addPreCommitTopology
```
DataStream<CommittableMessage<CommittableT>> addPreCommitTopology(DataStream<CommittableMessage<WriterResultT>> committables)
```
    Intercepts and modifies the committables sent on checkpoint or at end of input. Implementers need to ensure to modify all CommittableMessages appropriately.
    
    Parameters:
    
    committables - the stream of committables.
    
    Returns:
    
    the custom topology before Committer.
  - getWriteResultSerializer
```
org.apache.flink.core.io.SimpleVersionedSerializer<WriterResultT> getWriteResultSerializer()
```
    Returns the serializer of the WriteResult type.