code: public static LinkRelation parse(String relation) {
  
  		return LINK_RELATIONS.stream() //
  				.filter(it -> it.value().equalsIgnoreCase(relation)) //
  				.findFirst() //
  				.orElseThrow(() -> new IllegalArgumentException(relation + " is not a valid IANA link relation!"));
  	}
docs: Convert a string-based link relation to a {@link IanaLinkRelations}. Per RFC8288, parsing of link relations is case
  insensitive.
  
  @param relation as a string
  @return the link relation as a {@link LinkRelation}