@staticmethod
def collect_netdev():
    """collect cummulated network device Rx/Tx bytes"""
    with open('/proc/net/dev', 'r') as f:
        f.readline()
        f.readline()
        for net in f:
            net = net.split()
            interface, rx, tx = net[0][:-1], int(net[1]), int(net[9])
            yield interface, {'rx_data': rx, 'tx_data': tx}
