code: public static PublishDelete createPublishDelete(Identifier i1, String filter) {
  		return createPublishDelete(i1, null, filter);
  	}
docs: Create a new {@link PublishDelete} instance for a specific {@link Identifier}
  in order to delete its metadata that matches the given filter.
  
  @param i1 the {@link Identifier} that is the target of the delete request
  @param filter a filter that expresses the metadata that shall be deleted
  @return the new {@link PublishDelete} instance