code: def test_merge_importance_dfs_base(sample_features):
      # test the scenario when previous feature importance df is none
      prev_df, curr_df = None, unevaluated_fi_df_template(
          sample_features
      )
      assert (
          merge_importance_dfs(
              prev_df, curr_df, using_prev_fit_fi=set()
          )
          is curr_df
      )
  
file_path: autogluon/core/tests/unittests/test_feature_selection.py
imports: import numpy
  import pandas
  import pytest
  from numpy.core.fromnumeric import sort
  from autogluon.core.utils.feature_selection import *
  from autogluon.core.utils.utils import unevaluated_fi_df_template
label_desc: Use image node_id 6 for calling a global function with example usage: test_merge_importance_dfs_base(sample_features) without return types