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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 extract_mentions(self):
 """ Extract mentions from an entity with ``raw_content``. :return: set """

        if not hasattr(self, "raw_content"):
            return set()
        mentions = re.findall(r'@{[^;]+; [\w.-]+@[^}]+}', self.raw_content)
        if not mentions:
            return set()
        mentions = {s.split(';')[1].strip(' }') for s in mentions}
        mentions = {s for s in mentions}
        return mentions