code: public Pair<F, S> argMax() {
          Double maxCount = -Double.MAX_VALUE;
          Pair<F, S> maxKey = null;
          for (Map.Entry<F, Counter<S>> entry : maps.entrySet()) {
              Counter<S> counter = entry.getValue();
              S localMax = counter.argMax();
              if (counter.getCount(localMax) > maxCount || maxKey == null) {
                  maxKey = new Pair<F, S>(entry.getKey(), localMax);
                  maxCount = counter.getCount(localMax);
              }
          }
          return maxKey;
      }
docs: This method returns pair of elements with a max value
  
  @return