code: static <S extends Storable> BlobReplicationTrigger<S> create(Storage<S> masterStorage) {
          Map<String, ? extends StorableProperty<S>> properties = 
              StorableIntrospector.examine(masterStorage.getStorableType()).getDataProperties();
  
          List<String> blobNames = new ArrayList<String>(2);
  
          for (StorableProperty<S> property : properties.values()) {
              if (property.getType() == Blob.class) {
                  blobNames.add(property.getName());
              }
          }
  
          if (blobNames.size() == 0) {
              return null;
          }
  
          return new BlobReplicationTrigger<S>(masterStorage,
                                               blobNames.toArray(new String[blobNames.size()]));
      }
docs: Returns null if no Blobs need to be replicated.