code: def test_ardl_only_x(data):
      res = ARDL(
          data.y,
          None,
          data.x,
          {"lry": 1, "ibo": 2, "ide": 3},
          trend="n",
      ).fit()
      assert res.params.shape[0] == 9
      res = ARDL(
          data.y,
          None,
          data.x,
          {"lry": 1, "ibo": 2, "ide": 3},
          trend="n",
          causal=True,
      ).fit()
      assert res.params.shape[0] == 6
      check_results(res)
  
imports: from typing import NamedTuple
  import numpy
  from numpy.testing import assert_allclose
  import pandas
  from pandas.testing import assert_index_equal
  import pytest
  from statsmodels.datasets import danish_data
  from statsmodels.iolib.summary import Summary
  from statsmodels.tools.sm_exceptions import SpecificationWarning
  from statsmodels.tsa.ar_model import AutoReg
  from statsmodels.tsa.ardl.model import ARDL, UECM, ARDLResults, ardl_select_order
  from statsmodels.tsa.deterministic import DeterministicProcess
label_desc: Use image node_id 25 for calling a global function with example usage: test_ardl_only_x(data) without return types