code: def test_append_len_one(self, ri):
      # GH39401
      result = ri.append([])
      tm.assert_index_equal(result, ri, exact=True)
  
imports: import numpy
  import pytest
  from pandas.core.dtypes.common import ensure_platform_int
  import pandas
  from pandas import Index, RangeIndex
  import pandas._testing
label_desc: Use image node_id 39 for calling the TestRangeIndex obj's underlying member method code with example usage: obj.test_append_len_one(ri) without return types