code: def test_append_row_range(self):
      r_set = row_set.empty()
      r_set.append(row_range.closed_range("row1", "row2"))
      expected = (
          "row_ranges {\n"
          '  start_key_closed: "row1"\n'
          '  end_key_closed: "row2"\n'
          "}\n"
      )
      self.assertEqual(expected, repr(r_set))
  
imports: from tensorflow_io.python.ops import core_ops
  import tensorflow_io.python.ops.bigtable.bigtable_row_range
  import tensorflow_io.python.ops.bigtable.bigtable_row_set
  from tensorflow import test
label_desc: Use image node_id 3 for calling the TestRowSet obj's underlying member method code with example usage: obj.test_append_row_range() without return types