Close the KafkaAdminClient connection to the Kafka broker.

def close(self):
        """Close the KafkaAdminClient connection to the Kafka broker."""
        if not hasattr(self, '_closed') or self._closed:
            log.info("KafkaAdminClient already closed.")
            return

        self._metrics.close()
        self._client.close()
        self._closed = True
        log.debug("KafkaAdminClient is now closed.")