Why are some Tx objects not extended from AvaxTx or Transaction?

[hoangong]

For example CreateAssetTx.

The issue is that there is no consistent way to getInputs or serialize it using toBytes()

This is how I currently read the inputs

const inputs: avaxSerial.TransferableInput[] = [];
  // @ts-ignore
  if (transaction.unsignedTx.inputs) {
    // @ts-ignore
    inputs.push(...transaction.unsignedTx.inputs);
    // @ts-ignore
  } else if (transaction.unsignedTx.baseTx.inputs) {
    // @ts-ignore
    inputs.push(...transaction.unsignedTx.baseTx.inputs);
  }

and this is how I serialize

export function serializeSignedTx(tx: avaxSerial.SignedTx): Buffer {
  if (tx.unsignedTx.vm) {
    return Buffer.from(tx.toBytes());
  } else if (tx.unsignedTx._type.startsWith('avm.')) {
    return Buffer.from(
      utils.concatBytes(
        new Short(0).toBytes(),
        utils.getManagerForVM('AVM').codecs[0].PackPrefix(tx.unsignedTx),
        utils.getManagerForVM('AVM').codecs[0].PackPrefixList(tx.credentials),
      ),
    );
  } else {
    return Buffer.from(
      utils.concatBytes(
        new Short(0).toBytes(),
        utils.getManagerForVM('PVM').codecs[0].PackPrefix(tx.unsignedTx),
        utils.getManagerForVM('PVM').codecs[0].PackPrefixList(tx.credentials),
      ),
    );
  }
}

is there better way?