code: function(data, prefix) {
    prefix = prefix || '';
    var row = Object.keys(data).map(function(key) {
      if (typeof data[key] !== 'object') {
        return util.format('%s%s="%s"', prefix, key, data[key]);
      }
      // Flatten this nested object.
      return _reformat(data[key], key + '.');
    });
    return row.join(' ');
  }
docs: data - json object representation of a log line. prefix - string to prefix a key with. Used in flattening nested objects.  Returns a single string of concatenated key=value pairs.