code: def df():
      df = generate_df_for_tests(freq="D", periods=1000)["df"]
      return df
  
file_path: greykite/greykite/tests/algo/common/test_seasonality_inferrer.py
imports: from copy import deepcopy
  import pandas
  import pytest
  from greykite.algo.common.seasonality_inferrer import SeasonalityInferConfig
  from greykite.algo.common.seasonality_inferrer import SeasonalityInferrer
  from greykite.algo.common.seasonality_inferrer import TrendAdjustMethodEnum
  from greykite.common import constants
  from greykite.common.testing_utils import assert_equal
  from greykite.common.testing_utils import generate_df_for_tests
  from greykite.common.time_properties import infer_freq
label_desc: Use image node_id 1 for calling a global function with example usage: df() and returns: df