public void writeToOutputStream(DataOutputStream out) throws IOException {
            out.writeInt(map.size());
            for (LongObjectPair<int[]> p : map.keyValuesView()) {
                out.writeLong(p.getOne());
                SerializationHelper.writeIntArray(p.getTwo(), out);
            }
        }
A searchable index of conjunctions (see {@link FeatureConjunction} / {@link IndexableFeatureConjunction}).
Implements the algorithm described in the paper
<a href="http://dl.acm.org/citation.cfm?id=1687633">Indexing Boolean Expressions</a>.

@author Magnar Nedland
@author bjorncs
predicate-search/src/main/java/com/yahoo/search/predicate/index/conjunction/ConjunctionIndex.java