code: public Map<T, Double> getProbabilityMap() {
      Map<T, Double> probabilityMap = Maps.newHashMap();
      for (T item : counts.keySet()) {
        probabilityMap.put(item, getProbability(item));
      }
      return probabilityMap;
    }
docs: Gets the probabilities of the items in {@code this} as a
  {@code Map}. Each observed item is a key in the returned map, and
  its probability is the corresponding value.
  
  @return