code: def test_nonfull_periodindex():
      index = pd.PeriodIndex(["2000-01", "2000-03"], freq="M")
      endog = pd.Series(np.zeros(len(index)), index=index)
  
      message = (
          "A Period index has been provided, but it is not"
          " full and so will be ignored when e.g."
          " forecasting."
      )
      with pytest.warns(ValueWarning, match=message):
          tsa_model.TimeSeriesModel(endog)
  
imports: from statsmodels.compat.pandas import PD_LT_2_2_0, YEAR_END, is_int_index
  import warnings
  import numpy
  from numpy.testing import assert_equal, assert_raises
  import pandas
  import pytest
  from statsmodels.tools.sm_exceptions import ValueWarning
  from statsmodels.tsa.base import tsa_model
label_desc: Use image node_id 13 for calling a global function with example usage: test_nonfull_periodindex() without return types