public String[] toStrings(Recognizer<?, ?> recognizer, int currentState) {
		return toStrings(recognizer, EmptyPredictionContext.Instance, currentState);
	}
Make pass over all <em>M</em> {@code parents}; merge any {@code equals()}
ones.
runtime/Java/src/org/antlr/v4/runtime/atn/PredictionContext.java