public static List<PredictionContext> getAllContextNodes(PredictionContext context) {
		List<PredictionContext> nodes = new ArrayList<PredictionContext>();
		Map<PredictionContext, PredictionContext> visited =
			new IdentityHashMap<PredictionContext, PredictionContext>();
		getAllContextNodes_(context, nodes, visited);
		return nodes;
	}
Make pass over all <em>M</em> {@code parents}; merge any {@code equals()}
ones.
runtime/Java/src/org/antlr/v4/runtime/atn/PredictionContext.java