code: private void checkTagName(String name) {
          if (standardTags.contains(name)) {
              overridenStandardTags.add(name);
          } else {
              if (name.indexOf('.') == -1) {
                  potentiallyConflictingTags.add(name);
              }
              unseenCustomTags.add(name);
          }
      }
docs: Given a tag name, add it to the set of tags it belongs to.