protected void merge(int extProdNum, Collection<AssemblyTerminal> more) {
			extProds.add(extProdNum);
			this.follow.addAll(more);
		}
The map value keyed by {@link MergeKey}
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/assembler/sleigh/parse/AssemblyParser.java