MapTuple(fn) fails if fn has type hints but no default args

  def test_typed_maptuple(self):
    def fn(e1: int, e2: int) -> int:
      return e1 * e2

    result = [(1, 1), (2, 2)] | beam.MapTuple(fn)
    self.assertEqual([2, 4], sorted(result))

>       raise TypeCheckError(e)
E       apache_beam.typehints.decorators.TypeCheckError: too many positional arguments