js2xml: function(obj, parentKey, depth) {
  var self = this;
  var xml = '';
  depth = (depth == undefined ? 0 : depth + 1);

  var tabs = '';
  for (var i = 0; i < depth; i++) {
    tabs += '  ';
  }

  if (typeof obj == 'object') {
      _.each(obj, function(v, k) {
        var fn = _.bind(self._js2xml, self);
        if (obj instanceof Array) {
          k = parentKey + "_" + k;
        }
        xml += "\n" + tabs + "<" + k + ">" + fn(v, k, depth) +  "\n" + tabs + "</" + k + ">";
      });
  } else {
    xml += "\n" + tabs + obj;
  }
  return xml;
}