es_recv:   number of bytes received
 - packets_sent: number of packets sent
 - packets_recv: number of packets received
 - errin:        total number of errors while receiving
 - errout:       total number of errors while sending
 - dropin:       total number of incoming packets which were dropped
 - dropout:      total number of outgoing packets which were dropped
                 (always 0 on macOS and BSD)

If *pernic* is True return the same information for every
network interface installed on the system as a dictionary
with network interface names as the keys and the namedtuple
described above as the values.

If *nowrap* is True it detects and adjust the numbers which overflow
and wrap (restart from 0) and add "old value" to "new value" so that
the returned numbers will always be increasing or remain the same,
but never decrease.
"net_io_counters.cache_clear()" can be used to invalidate the
cache.
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