docs: public static int getTwoWordFreq(Term from, Term to) {
          if (from.item().bigramEntryMap == null) {
              return 0;
          }
          Integer freq = from.item().bigramEntryMap.get(to.item().getIndex());
          if (freq == null) {
              return 0;
          } else {
              return freq;
          }
      }