code: def test_init():
      """Tests instantiation."""
      model = SeasonalityInferrer()
      assert model.df is None
      assert model.time_col is None
      assert model.value_col is None
      assert model.fourier_series_orders is None
      assert model.FITTED_TREND_COL == "FITTED_TREND"
  
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 4 for calling a global function with example usage: test_init() without return types