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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 get_domain_resolver(self, domain_name, cur=None):
 """ Get the last-knwon resolver entry for a domain name Returns None if not found. """

        get_cmd = "SELECT resolver FROM {} WHERE domain=? AND resolver != '' AND accepted=1 ORDER BY sequence DESC, parent_zonefile_index DESC LIMIT 1;".format(self.subdomain_table)

        cursor = None
        if cur is None:
            cursor = self.conn.cursor()
        else:
            cursor = cur

        db_query_execute(cursor, get_cmd, (domain_name,))

        rowdata = cursor.fetchone()
        if not rowdata:
            return None

        return rowdata['resolver']