Hey so I was running a local node and trying explorer/polkadot.js-scripts to submit some extrinsic and from what I have seen from the data log, I have seen that something is being appended before the original data. Like I have seen that its scale enocoded and the length of vector is there, but there's more to it! Not sure what all being inside the extrinsic struct. I have got a struct from gsrpc extrinsic struct. I don't know if this is what I'm looking for. So can I have some reference on what struct of extrinsic is being used in polkadot-js or what is being added to the original data.