@Override
	public boolean isEpsilon() { return true; }
TODO: this is old comment:
 A tree of semantic predicates from the grammar AST if label==SEMPRED.
 In the ATN, labels will always be exactly one predicate, but the DFA
 may have to combine a bunch of them as it collects predicates from
 multiple ATN configurations into a single DFA state.
runtime/Java/src/org/antlr/v4/runtime/atn/PredicateTransition.java