code: public void addLegacyTagIdMappings(String tagId, String tagName)
      {
          assert (tagId != null) : "The parameter 'tagId' must not be null";
          assert (tagName != null) : "The parameter 'tagName' must not be null";
  
          if (_idMap == null) {
              _idMap = new HashMap/*<String, String>*/();
          }
  
          assert (_idMap != null) : "_idMap should not be null";
          _idMap.put(tagId, tagName);
      }
docs: Adds a tagID and tagName to the Html's getId javascript function.
  @param tagId   the id of a child tag.
  @param tagName the name of a child tag.