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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 sql_like_fragments(self) -> List[str]: """ Returns all the string literals to which a database column should be compared using the SQL ``LIKE`` operator, to match this drug. This isn't as accurate as the regex, but ``LIKE`` can do less. ``LIKE`` uses the wildcards ``?`` and ``%``. """

        if self._sql_like_fragments is None:
            self._sql_like_fragments = []
            for p in list(set(self.all_generics + self.alternatives)):
                self._sql_like_fragments.extend(self.regex_to_sql_like(p))
        return self._sql_like_fragments