@Override
    protected Function<Object,T> keyConverter(){
        return o -> {
            throw new UnsupportedOperationException(String.format("%s cannot be converted", o==null?"null":o.getClass()));
        };
    }
@ Override protected Function < Object , T > keyConverter ( ) { return o -> { throw new UnsupportedOperationException ( String . format ( "%s cannot be converted" , o == null ? "null" : o . getClass ( ) ) ) ; } ; }
@return the converter used to convert the returned primary key to type T. Since the input argument of the Function
is always a {@code Long} (in MYSQL mode), only non-compound numeric keys can be returned. This method gets automatically overridden during
DAO-creation depending on T.