code: func (r *Request) fromChunk(chunk storage.Chunk) error {
  	// for update chunk layout see Request definition
  
  	chunkdata := chunk.Data()
  
  	//deserialize the feed update portion
  	if err := r.Update.binaryGet(chunkdata[:len(chunkdata)-signatureLength]); err != nil {
  		return err
  	}
  
  	// Extract the signature
  	var signature *Signature
  	cursor := r.Update.binaryLength()
  	sigdata := chunkdata[cursor : cursor+signatureLength]
  	if len(sigdata) > 0 {
  		signature = &Signature{}
  		copy(signature[:], sigdata)
  	}
  
  	r.Signature = signature
  	r.idAddr = chunk.Address()
  	r.binaryData = chunkdata
  
  	return nil
  
  }
docs: // fromChunk populates this structure from chunk data. It does not verify the signature is valid.