code: func writeTxWitness(w io.Writer, pver uint32, version int32, wit [][]byte) error {
  	err := WriteVarInt(w, pver, uint64(len(wit)))
  	if err != nil {
  		return err
  	}
  	for _, item := range wit {
  		err = WriteVarBytes(w, pver, item)
  		if err != nil {
  			return err
  		}
  	}
  	return nil
  }
docs: // writeTxWitness encodes the bitcoin protocol encoding for a transaction
  // input's witness into to w.