code: function(seed, cb) {
      var self = this;
  
      utils.safeExec('uname -a', function(err, uname) {
        var userAgent = {};
        for (var field in seed) {
          userAgent[field] = encodeURIComponent(seed[field]);
        }
  
        // URI-encode in case there are unusual characters in the system's uname.
        userAgent.uname = encodeURIComponent(uname || 'UNKNOWN');
  
        if (self._appInfo) {
          userAgent.application = self._appInfo;
        }
  
        cb(JSON.stringify(userAgent))
      });
    }
docs: Gets a JSON version of a User-Agent by encoding a seeded object and fetching a uname from the system.