code: func CliqueRLP(header *types.Header) []byte {
  	b := new(bytes.Buffer)
  	encodeSigHeader(b, header)
  	return b.Bytes()
  }
docs: // CliqueRLP returns the rlp bytes which needs to be signed for the proof-of-authority
  // sealing. The RLP to sign consists of the entire header apart from the 65 byte signature
  // contained at the end of the extra data.
  //
  // Note, the method requires the extra data to be at least 65 bytes, otherwise it
  // panics. This is done to avoid accidentally using both forms (signature present
  // or not), which could be abused to produce different hashes for the same header.