code: function build (obj, opts) {
    var XMLHDR = {
      version: '1.0',
      encoding: 'UTF-8'
    };
  
    var XMLDTD = {
      pubid: '-//Apple//DTD PLIST 1.0//EN',
      sysid: 'http://www.apple.com/DTDs/PropertyList-1.0.dtd'
    };
  
    var doc = xmlbuilder.create('plist');
  
    doc.dec(XMLHDR.version, XMLHDR.encoding, XMLHDR.standalone);
    doc.dtd(XMLDTD.pubid, XMLDTD.sysid);
    doc.att('version', '1.0');
  
    walk_obj(obj, doc);
  
    if (!opts) opts = {};
    // default `pretty` to `true`
    opts.pretty = opts.pretty !== false;
    return doc.end(opts);
  }
docs: Generate an XML plist string from the input object `obj`.
  
  @param {Object} obj - the object to convert
  @param {Object} [opts] - optional options object
  @returns {String} converted plist XML string
  @api public