code: function appendStream(streams, s) {
      assert.arrayOfObject(streams, 'streams');
      assert.object(s, 'stream');
  
      if (s instanceof Stream) {
          streams.push({
              raw: false,
              stream: s
          });
      } else {
          assert.optionalBool(s.raw, 'stream.raw');
          assert.object(s.stream, 'stream.stream');
          streams.push(s);
      }
  }
docs: --- Helpers 
  appends streams
  @private
  @function appendStream
  @param    {Stream}    streams the stream to append to
  @param    {Stream}    s       the stream to append
  @returns  {undefined}