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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 flush_all(self, conn):
 """Its effect is to invalidate all existing items immediately"""

        command = b'flush_all\r\n'
        response = yield from self._execute_simple_command(
            conn, command)

        if const.OK != response:
            raise ClientException('Memcached flush_all failed', response)