code: def test_build_agg_lag_df_col_names_only():
      """Testing build_agg_lag_df for the case where input df is not passed and
      only col_names are generated"""
  
      agg_lag_info = build_agg_lag_df(
          value_col="x",
          df=None,
          orders_list=[[1, 2, 5], [1, 3, 8], [2, 3, 4]],
          interval_list=[(1, 5), (1, 8)],
          agg_func=np.mean,
          agg_name="avglag",
      )
  
      col_names = agg_lag_info["col_names"]
  
      assert col_names == [
          "x_avglag_1_2_5",
          "x_avglag_1_3_8",
          "x_avglag_2_3_4",
          "x_avglag_1_to_5",
          "x_avglag_1_to_8",
      ], "aggregated lag df does not have the correct names"
  
      assert (
          agg_lag_info["agg_lag_df"] is None
      ), "returned agg_lag_df must be None"
  
imports: import numpy
  import pandas
  import pytest
  from greykite.common.features.timeseries_lags import build_agg_lag_df
  from greykite.common.features.timeseries_lags import build_autoreg_df
  from greykite.common.features.timeseries_lags import build_autoreg_df_multi
  from greykite.common.features.timeseries_lags import build_lag_df
  from greykite.common.features.timeseries_lags import min_max_lag_order
  from greykite.common.python_utils import assert_equal
label_desc: Use image node_id 6 for calling a global function with example usage: test_build_agg_lag_df_col_names_only() without return types