code: public boolean isArray(final String rel) {
          final String resolvedRel = curies.resolve(rel);
          return hasItem(rel) && (items.get(resolvedRel) instanceof List);
      }
docs: Returns true if there is at least one embedded item with link-relation type {@code rel}, and if the item will
  be rendered as an array of embedded items instead of a single object.
  
  @param rel the link-relation type
  @return boolean
  
  @since 2.0.0