code: func bitsetEncodeBytes(data []byte) []byte {
  	// Empty slices get compressed to nil
  	if len(data) == 0 {
  		return nil
  	}
  	// One byte slices compress to nil or retain the single byte
  	if len(data) == 1 {
  		if data[0] == 0 {
  			return nil
  		}
  		return data
  	}
  	// Calculate the bitset of set bytes, and gather the non-zero bytes
  	nonZeroBitset := make([]byte, (len(data)+7)/8)
  	nonZeroBytes := make([]byte, 0, len(data))
  
  	for i, b := range data {
  		if b != 0 {
  			nonZeroBytes = append(nonZeroBytes, b)
  			nonZeroBitset[i/8] |= 1 << byte(7-i%8)
  		}
  	}
  	if len(nonZeroBytes) == 0 {
  		return nil
  	}
  	return append(bitsetEncodeBytes(nonZeroBitset), nonZeroBytes...)
  }
docs: // bitsetEncodeBytes compresses the input byte slice according to the sparse
  // bitset representation algorithm.