<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def lookup_char(self, char):
 """Return character information from datasets. Parameters char : str character / string to lookup Returns ------- :class:`sqlalchemy.orm.query.Query` : list of matches """

        Unihan = self.sql.base.classes.Unihan
        return self.sql.session.query(Unihan).filter_by(char=char)