code: public DatastreamVersion copy() {
          DatastreamVersion copy = new DatastreamVersion(id,
                                                         Util.copy(createdDate))
                  .label(label)
                  .mimeType(mimeType)
                  .formatURI(formatURI)
                  .size(size)
                  .contentDigest(contentDigest == null ? null : contentDigest.copy())
                  .inlineXML(inlineXML)
                  .contentLocation(contentLocation);
          copy.altIds().addAll(altIds);
          return copy;
      }
docs: Creates an instance based on the current state of this one.
  
  @return a deep copy.