code: public static Hop rel(String rel) {
  
  		Assert.hasText(rel, "Relation must not be null or empty!");
  
  		return new Hop(rel, Collections.emptyMap(), HttpHeaders.EMPTY);
  	}
docs: Creates a new {@link Hop} for the given relation name.
  
  @param rel must not be {@literal null} or empty.
  @return