<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _drop_tables(self):
 """ Clear the subdomain db's tables """

        drop_cmd = "DROP TABLE IF EXISTS {};"
        for table in [self.subdomain_table, self.blocked_table]:
            cursor = self.conn.cursor()
            db_query_execute(cursor, drop_cmd.format(table), ())