code: public static Optional<IRI> get(IRI nextIRI) {
  		for (IRI nextType : values()) {
  			if (nextType.equals(nextIRI)) {
  				return Optional.of(nextType);
  			}
  		}
  		return Optional.empty();
  	}
docs: Get the IRI from this collection if it is present, or return
  {@link Optional#empty()} otherwise.
  
  @param nextIRI
  The IRI to look for.
  @return An {@link Optional} containing the IRI from this collection or
  {@link Optional#empty()} if it is not present here.