code: public <T extends Type & Element> void register(String fullyQualifiedName, T type) {
          if (resolve(fullyQualifiedName) != null) {
              throw new ParserException(type, "Cannot register duplicate type: %s", fullyQualifiedName);
          }
          symbolTable.put(fullyQualifiedName, type);
      }
docs: Register user type in symbol table. Full name should start with ".".