code: public PartitionAwareDataWriterBuilder<S, D> forPartition(GenericRecord partition) {
      this.partition = Optional.fromNullable(partition);
      log.debug("For partition {}", this.partition);
      return this;
    }
docs: Sets the partition that the build {@link DataWriter} will handle.
  @param partition A {@link GenericRecord} specifying the partition.
  @return A {@link PartitionAwareDataWriterBuilder}.