code: def a_step_function():
      x = np.array([0, 1, 1.2, 1.75, 2, 2.1, 3, 3.94, 5.4, 9])
      y = np.array([11, 9, 9.12, 7.5, 7.25, 5.14, 3, 2.94, 2.4, 1.9])
      f = StepFunction(x, y)
      return f
  
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 1 for calling a global function with example usage: a_step_function() and returns: f