function docker_calcNetworkIO(networks) {
  let rx;
  let wx;
  for (let key in networks) {
    // skip loop if the property is from prototype
    if (!{}.hasOwnProperty.call(networks, key)) { continue; }

    /**
     * @namespace
     * @property {number}  rx_bytes
     * @property {number}  tx_bytes
     */
    let obj = networks[key];
    rx = +obj.rx_bytes;
    wx = +obj.tx_bytes;
  }
  return {
    rx,
    wx
  };
}
@namespace
@property {object}  cpu_usage
@property {number}  cpu_usage.total_usage
@property {number}  system_cpu_usage
@property {object}  cpu_usage
@property {Array}  cpu_usage.percpu_usage