code: def nan_float_array():
      penalty = np.zeros(30)
      penalty[11] = np.nan
      return penalty
  
imports: from dataclasses import dataclass
  from os.path import dirname, join
  from typing import Optional
  import numpy
  from numpy.testing import assert_array_almost_equal
  import pandas
  import pytest
  from sklearn.exceptions import ConvergenceWarning
  from sklearn.pipeline import make_pipeline
  from sksurv.datasets import get_x_y, load_breast_cancer
  from sksurv.linear_model.coxnet import CoxnetSurvivalAnalysis
  from sksurv.preprocessing import OneHotEncoder
  from sksurv.testing import FixtureParameterFactory
  from sksurv.util import Surv
label_desc: Use image node_id 4 for calling a global function with example usage: nan_float_array() and returns: penalty