code: @Override
      public String writeSingle(String spaceId,
                                String chunkChecksum,
                                ChunkInputStream chunk,
                                Map<String, String> properties)
          throws NotFoundException {
  
          log.debug("writeSingle: " + spaceId + ", " + chunk.getChunkId());
          createSpaceIfNotExist(spaceId);
  
          addChunk(spaceId, chunkChecksum, chunk, properties, true);
  
          log.debug("written: " + spaceId + ", " + chunk.getChunkId());
          return chunk.getMD5();
      }
docs: This method writes a single chunk to the DataStore.
  
  @param spaceId       destination where arg chunk content will be written
  @param chunkChecksum md5 checksum of the chunk if known, null otherwise
  @param chunk         content to be written
  @param properties    user-defined properties for the content
  @return MD5 of written content
  @throws NotFoundException if space is not found