protected void decodeHeader(Decoder decoder) throws DecoderException {
		index = (int) decoder.readSignedInteger(ATTRIB_INDEX);
	}
Encode basic attributes to stream. Assume this block's element is already started.
@param encoder is the stream encoder
@throws IOException for errors writing to the underlying stream
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/PcodeBlock.java