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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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()