code: @SuppressWarnings("unchecked")
    @NonNull public CMARichBlock addContent(@NonNull CMARichNode... content) {
      if (content == null) {
        throw new NullPointerException("content is null");
      }
  
      this.content.addAll(Arrays.asList(content));
  
      return this;
    }
docs: adds content to the already existing content.
  
  @param content elements to be added.
  @return this instance for chaining.