def get_queryset(self):
        """
        Retrieve the author by his username and
        build a queryset of his published entries.
        """
        self.author = get_object_or_404(
            Author, **{Author.USERNAME_FIELD: self.kwargs['username']})
        return self.author.entries_published()
Retrieve the author by his username and
        build a queryset of his published entries.