code: def test_power_under_cph():
      assert (
          abs(stats.power_under_cph(12, 12, 0.8, 0.2, 0.139) - 0.744937)
          < 10e-6
      )
      assert (
          abs(stats.power_under_cph(12, 20, 0.8, 0.2, 1.2) - 0.05178317)
          < 10e-6
      )
  
imports: import numpy
  import pandas
  import numpy.testing
  import pytest
  from pandas.testing import assert_frame_equal
  from lifelines import statistics
  from lifelines import CoxPHFitter, KaplanMeierFitter, WeibullFitter
  from lifelines.exceptions import StatisticalWarning
  from lifelines.datasets import load_waltons, load_g3, load_lymphoma, load_dd, load_regression_dataset, load_leukemia
label_desc: Use image node_id 2 for calling a global function with example usage: test_power_under_cph() without return types