code: public MutationState add(DocumentFragment... documentFragments) {
          if (documentFragments == null || documentFragments.length == 0) {
              throw new IllegalArgumentException("At least one DocumentFragment must be provided.");
          }
          for (DocumentFragment d : documentFragments) {
              addToken(d.mutationToken());
          }
          return this;
      }
docs: Add one or more {@link DocumentFragment DocumentFragments} to this {@link MutationState}.
  
  @param documentFragments the fragments where the tokens are extracted from.
  @return the modified {@link MutationState}.