code: def test_ndiffs_stationary():
      # show that for a stationary vector, ndiffs returns 0
      x = np.ones(10)
      assert ndiffs(x, alpha=0.05, test="kpss", max_d=2) == 0
      assert ndiffs(x, alpha=0.05, test="pp", max_d=2) == 0
      assert ndiffs(x, alpha=0.05, test="adf", max_d=2) == 0
  
file_path: pmdarima/pmdarima/arima/tests/test_stationarity.py
imports: from pmdarima.arima.stationarity import ADFTest, PPTest, KPSSTest
  from pmdarima.arima.utils import ndiffs
  from pmdarima.utils.array import diff
  from pmdarima.datasets import load_austres
  from sklearn.utils import check_random_state
  from numpy.testing import assert_array_almost_equal, assert_almost_equal, assert_array_equal
  import numpy
  import pytest
label_desc: Use image node_id 1 for calling a global function with example usage: test_ndiffs_stationary() without return types