code: void buildPT_T() {
      int numTags = tagIndex.size();
      m_TT = new double[numTags][numTags];
      m_T = new double[numTags];
      double[] tmp = new double[numTags];
      for (IntTaggedWord word : words) {
        double tot = 0.0;
        for (int t = 0; t < numTags; t++) {
          IntTaggedWord iTW = new IntTaggedWord(word.word, t);
          tmp[t] = seenCounter.getCount(iTW);
          tot += tmp[t];
        }
        if (tot < 10) {
          continue;
        }
        for (int t = 0; t < numTags; t++) {
          for (int t2 = 0; t2 < numTags; t2++) {
            if (tmp[t2] > 0.0) {
              double c = tmp[t] / tot;
              m_T[t] += c;
              m_TT[t2][t] += c;
            }
          }
        }
      }
    }
docs: This records how likely it is for a word with one tag to also have another
  tag. This won't work after serialization/deserialization, but that is how
  it is currently called....