code: public static int getIdFor(Class<? extends Tag> clazz) {
          if(!tagToId.containsKey(clazz)) {
              return -1;
          }
  
          return tagToId.get(clazz);
      }
docs: Gets the id of the given tag class.
  
  @param clazz The tag class to get the id of.
  @return The id of the given tag class, or -1 if it cannot be found.