docs: 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