code: public static ConstructorRef create(TypeInfo type, Method init) {
      checkArgument(
          init.getName().equals("<init>") && init.getReturnType().equals(Type.VOID_TYPE),
          "'%s' is not a valid constructor",
          init);
      return new AutoValue_ConstructorRef(type, init, ImmutableList.copyOf(init.getArgumentTypes()));
    }
docs: Returns a new {@link ConstructorRef} that refers to a constructor on the given type with the
  given parameter types.