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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 authors_et_al(self, max_authors=5):
 """ Return string with a truncated author list followed by 'et al.' """

        author_list = self._author_list
        if len(author_list) <= max_authors:
            authors_et_al = self.authors
        else:
            authors_et_al = ", ".join(
                self._author_list[:max_authors]) + ", et al."
        return authors_et_al