code: private void genOptTypeArguments(List<? extends TypeMirror> typeArguments, StringBuilder sb) {
      if (!typeArguments.isEmpty()) {
        sb.append('<');
        for (TypeMirror typeParam : typeArguments) {
          genTypeSignature(typeParam, sb);
        }
        sb.append('>');
      }
    }
docs: OptTypeArguments ::= "<" TypeArgument {TypeArgument} ">".