docs: protected static Class mapTypeahead(Class c) {
      if(c != null) {
        if( PCAModel.class.isAssignableFrom(c) )
          return TypeaheadPCAModelKeyRequest.class;
        if( NBModel.class.isAssignableFrom(c) )
          return TypeaheadNBModelKeyRequest.class;
        if( Model.class.isAssignableFrom(c))
          return TypeaheadModelKeyRequest.class;
        if( Frame.class.isAssignableFrom(c) )
          return TypeaheadHexKeyRequest.class;
      }
      return TypeaheadKeysRequest.class;
    }