code: def test_append_empty(self, ci):
      # empty
      result = ci.append([])
      tm.assert_index_equal(result, ci, exact=True)
  
file_path: pandas/pandas/tests/indexes/categorical/test_append.py
imports: import pytest
  from pandas import CategoricalIndex, Index
  import pandas._testing
label_desc: Use image node_id 3 for calling the TestAppend obj's underlying member method code with example usage: obj.test_append_empty(ci) without return types