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