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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_documents(self, subtypes=None, refresh=False):
 """Return list of author's publications using ScopusSearch, which fit a specified set of document subtypes. """

        search = ScopusSearch('au-id({})'.format(self.identifier), refresh)
        if subtypes:
            return [p for p in search.results if p.subtype in subtypes]
        else:
            return search.results