pub fn get_rlp(&self) -> Result<Vec<u8>, SerializationTransactionError> {
        let mut rlp_stream = RlpStream::new();
        self.rlp(&mut rlp_stream, None)?;
        Ok(rlp_stream.as_raw().into())
    }
Encodes `TransactionRequest` to RLP.
It may fail if `chain_id` is `None` while required.
core/lib/types/src/transaction_request.rs