code: def test_not_exact(a_step_function):
      z = np.diff(a_step_function.x).min() / 2
      actual = np.array(
          [a_step_function(v + z) for v in a_step_function.x[:-1]]
      )
      assert_array_equal(actual, a_step_function.y[:-1])
  
file_path: scikit-survival/tests/test_functions.py
imports: import numpy
  from numpy.testing import assert_array_equal
  import pytest
  from sksurv.functions import StepFunction
  from sksurv.testing import all_survival_estimators
label_desc: Use image node_id 2 for calling the TestStepFunction obj's underlying member method code with example usage: obj.test_not_exact(a_step_function) without return types