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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 with_fields(self, *fields):
 """Returns list of characters with information for certain fields. Parameters *fields : list of str fields for which information should be available Returns ------- :class:`sqlalchemy.orm.query.Query` : list of matches """

        Unihan = self.sql.base.classes.Unihan
        query = self.sql.session.query(Unihan)
        for field in fields:
            query = query.filter(Column(field).isnot(None))
        return query