public static Collection<BitSet> getConflictingAltSubsets(ATNConfigSet configs) {
		AltAndContextMap configToAlts = new AltAndContextMap();
		for (ATNConfig c : configs) {
			BitSet alts = configToAlts.get(c);
			if ( alts==null ) {
				alts = new BitSet();
				configToAlts.put(c, alts);
			}
			alts.set(c.alt);
		}
		return configToAlts.values();
	}
This function gets the conflicting alt subsets from a configuration set.
For each configuration {@code c} in {@code configs}:

<pre>
map[c] U= c.{@link ATNConfig#alt alt} # map hash/equals uses s and x, not
alt and not pred
</pre>
runtime/Java/src/org/antlr/v4/runtime/atn/PredictionMode.java