code: public Map<String, String> getTags() {
          Map<String, String> distilledTags = new HashMap<String, String>();
  
          for (Map.Entry<String, String> entry : potentialTags.entrySet()) {
              String key = entry.getKey();
              String value = entry.getValue();
  
              if (tagCounts.get(key).equals(totalAdds)) {
                  distilledTags.put(key, value);
              }
          }
          return distilledTags;
      }
docs: The common tags.
  
  @return  the common tags, empty map if none are common.