code: public static FullTextIndex fullTextIndex(@NonNull FullTextIndexItem... items) {
          if (items == null) {
              throw new IllegalArgumentException("items cannot be null.");
          }
          return new FullTextIndex(items);
      }
docs: Create a full-text search index with the given index item and options. Typically the index item is
  the property that is used to perform the match operation against with.
  
  @param items The index items.
  @return The full-text search index.