code: @JsonProperty
    @Deprecated
    public SeekableStreamEndSequenceNumbers<Integer, Long> getStartPartitions()
    {
      // Converting to start sequence numbers. This is allowed for Kafka because the start offset is always inclusive.
      final SeekableStreamStartSequenceNumbers<Integer, Long> startSequenceNumbers = getStartSequenceNumbers();
      return new SeekableStreamEndSequenceNumbers<>(
          startSequenceNumbers.getStream(),
          startSequenceNumbers.getPartitionSequenceNumberMap()
      );
    }
docs: This method is for compatibilty so that newer version of KafkaIndexTaskIOConfig can be read by
  old version of Druid. Note that this method returns end sequence numbers instead of start. This is because
  {@link SeekableStreamStartSequenceNumbers} didn't exist before.