private void makeAssociation(DataVertex op, DataVertex var, DataVertex assoc, int assocSlot) {
		Associate key = new Associate(assoc, assocSlot);
		ArrayList<DataVertex> assocList = associates.get(key);
		if (assocList == null) {
			assocList = new ArrayList<>();
			associates.put(key, assocList);
		}
		assocList.add(op);
		assocList.add(var);
	}
Make an association between an (op,var) node pair that has been removed from the graph, with
a node that remains in the graph.
@param op is the operation node being removed
@param var is the variable node being removed
@param assoc is the node to associate with
@param assocSlot is other distinguishing info about the association (incoming slot)
Ghidra/Features/CodeCompare/src/main/java/ghidra/features/codecompare/graphanalysis/DataGraph.java