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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 _cx_counters_psutil(self, tags=None):
 """ Collect metrics about interfaces counters using psutil """

        tags = [] if tags is None else tags
        for iface, counters in iteritems(psutil.net_io_counters(pernic=True)):
            metrics = {
                'bytes_rcvd': counters.bytes_recv,
                'bytes_sent': counters.bytes_sent,
                'packets_in.count': counters.packets_recv,
                'packets_in.error': counters.errin,
                'packets_out.count': counters.packets_sent,
                'packets_out.error': counters.errout,
            }
            self._submit_devicemetrics(iface, metrics, tags)