public void removeDescendant(PcodeOp op) {
		ListIterator<PcodeOp> iter = descend.listIterator();
		while (iter.hasNext()) {
			if (op == iter.next()) {
				iter.remove();
			}
		}
	}
This type of Varnode is a node in an Abstract Syntax Tree
It keeps track of its defining PcodeOp (in-edge) and PcodeOps which use it (out-edges)
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/VarnodeAST.java