code: def test_first_valid_index_empty(self, empty):
      # GH#12800
      assert empty.last_valid_index() is None
      assert empty.first_valid_index() is None
  
file_path: pandas/pandas/tests/frame/methods/test_first_valid_index.py
imports: import numpy
  import pytest
  from pandas import DataFrame, Index, Series, date_range
label_desc: Use image node_id 2 for calling the TestFirstValidIndex obj's underlying member method code with example usage: obj.test_first_valid_index_empty(empty) without return types