@Override
	protected void encodeHeader(Encoder encoder) throws IOException {
		super.encodeHeader(encoder);
		encoder.writeSignedInteger(AttributeId.ATTRIB_ALTINDEX, altindex);
	}
@return the alternative index, used as an id for the original basic block Object
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/BlockCopy.java