code: func AppendDeflateBytesLevel(dst, src []byte, level int) []byte {
  	w := &byteSliceWriter{dst}
  	WriteDeflateLevel(w, src, level)
  	return w.b
  }
docs: // AppendDeflateBytesLevel appends deflated src to dst using the given
  // compression level and returns the resulting dst.
  //
  // Supported compression levels are:
  //
  //    * CompressNoCompression
  //    * CompressBestSpeed
  //    * CompressBestCompression
  //    * CompressDefaultCompression
  //    * CompressHuffmanOnly