code: def test_add_lags_correct_df(test_df):
      expected = pd.DataFrame(
          {"X1": [1, 2], "X2": ["178", "154"], "X1-1": [0, 1]}
      )
      ans = add_lags(test_df, "X1", -1)
      assert (ans.columns == expected.columns).all()
      assert (ans.values == expected.values).all()
  
imports: import logging
  import numpy
  import pandas
  import pytest
  from sklego.pandas_utils import _add_lagged_numpy_columns, _add_lagged_pandas_columns, add_lags, log_step, log_step_extra
label_desc: Use image node_id 4 for calling a global function with example usage: test_add_lags_correct_df(test_df) without return types