@Override
	public boolean add(ATNConfig config) {
		return add(config, null);
	}
Indicates that this configuration set is part of a full context
 LL prediction. It will be used to determine how to merge $. With SLL
 it's a wildcard whereas it is not for LL context merge.
runtime/Java/src/org/antlr/v4/runtime/atn/ATNConfigSet.java