code: function createTorrent (input, opts, cb) {
    if (typeof opts === 'function') [ opts, cb ] = [ cb, opts ]
    opts = opts ? Object.assign({}, opts) : {}
  
    _parseInput(input, opts, (err, files, singleFileTorrent) => {
      if (err) return cb(err)
      opts.singleFileTorrent = singleFileTorrent
      onFiles(files, opts, cb)
    })
  }
docs: Create a torrent.
  @param  {string|File|FileList|Buffer|Stream|Array.<string|File|Buffer|Stream>} input
  @param  {Object} opts
  @param  {string=} opts.name
  @param  {Date=} opts.creationDate
  @param  {string=} opts.comment
  @param  {string=} opts.createdBy
  @param  {boolean|number=} opts.private
  @param  {number=} opts.pieceLength
  @param  {Array.<Array.<string>>=} opts.announceList
  @param  {Array.<string>=} opts.urlList
  @param  {function} cb
  @return {Buffer} buffer of .torrent file data