code: def test_no_freq():
      idx = pd.date_range("2000-1-1", periods=300)
      locs = []
      for i in range(100):
          locs.append(2 * i + int((i % 2) == 1))
      y = pd.Series(np.random.standard_normal(100), index=idx[locs])
      with pytest.raises(
          ValueError, match="You must specify a period or"
      ):
          ThetaModel(y)
  
file_path: statsmodels/statsmodels/tsa/forecasting/tests/test_theta.py
imports: from itertools import product
  import numpy
  import pandas
  import pytest
  from statsmodels.tsa.forecasting.theta import ThetaModel
label_desc: Use image node_id 5 for calling a global function with example usage: test_no_freq() without return types