public static BitSet getAlts(Collection<BitSet> altsets) {
		BitSet all = new BitSet();
		for (BitSet alts : altsets) {
			all.or(alts);
		}
		return all;
	}
Gets the complete set of represented alternatives for a collection of
alternative subsets. This method returns the union of each {@link BitSet}
in {@code altsets}.

@param altsets a collection of alternative subsets
@return the set of represented alternatives in {@code altsets}
runtime/Java/src/org/antlr/v4/runtime/atn/PredictionMode.java