code: protected void addContentType(ContentType contentType) throws DuplicateObjectException {
  
      String id = contentType.getId();
      if (this.id2contentTypeMap.containsKey(id)) {
        throw new DuplicateObjectException(contentType, id);
      }
      this.id2contentTypeMap.put(id, contentType);
    }
docs: This method registers the given {@code contentType} in this {@link ContentTypeManager}.
  
  @see #getContentType(String)
  
  @param contentType is the {@link ContentType} to add.
  @throws DuplicateObjectException if a {@link ContentType} with the same {@link ContentType#getId() ID} has already
  been registered.