code: @Override
      public boolean isFileExtensionRegistered(String fileTypeExtension) throws OSException {
          try {
              getFileExtension(fileTypeExtension);
              return true;
          } catch (OSException e) {
              return false;
          }
      }
docs: Checks if the given extension is already registered.
  
  @param fileTypeExtension File extension with leading dot, e.g.
  <code>.bar</code>.
  @return <code>true</code> if extension is registered, <code>false</code>
  otherwise.
  @throws OSException