@Override
  public byte[] call(final byte[] memento) throws IOException {
    try (final DataOutputStream outputStream = outputStreamProvider.create("hello")) {
      outputStream.writeBytes("Hello REEF!");
    }
    return null;
  }
@ Override public byte [ ] call ( final byte [ ] memento ) throws IOException { try ( final DataOutputStream outputStream = outputStreamProvider . create ( "hello" ) ) { outputStream . writeBytes ( "Hello REEF!" ) ; } return null ; }
Receives an output stream from the output service and writes "Hello REEF!" on it.

@param memento the memento objected passed down by the driver.
@return null
@throws java.io.IOException