class ExtraColumnsMetaDataProvider implements MetaDataProvider {

    @Override
    public boolean hasKey(String key)
    {
        return myExtraColumns.containsKey(key) || myOriginal.hasKey(key);
    }

    protected  ExtraColumnsMetaDataProvider(ExtraColumnsMetaDataProvider source);
    public  ExtraColumnsMetaDataProvider(MetaDataProvider original, Map<String, Object> extraColumns);

}