code: function(opts, force){
      force = process.env.CI ? false : force;
  
      if (!force && !config.enabled || !opts.event) return;
  
      var visitor = hostVisitor;
      var uid = machineID;
      var group = opts.group || 'default';
  
      if (opts.sessionID) {
          uid = opts.sessionID;
          visitor = ua(config.trackingId, uid, {strictCidFormat: false});
      }
  
      log.trace('track event', group + ':' + opts.event);
      log.trace('as a visitor', visitor);
  
      visitor.event({
          ec: group,
          ea: opts.event,
          ds: machineID,
          cs: machineID,
          cid: uid,
          uid: uid
      }).send();
  }
docs: Track host-initiated events (by unique machine id)