@Override
  public byte readByte() {
    checkElt("byte", 1);
    final byte b = payloadByte(0);
    setTo(nextItem());
    return b;
  }
Sets the input to the item provided (an offset to the beginning of an item) and check this is
valid.

@param item the value to which the current item is to be set.
ethereum/rlp/src/main/java/org/hyperledger/besu/ethereum/rlp/AbstractRLPInput.java