code: def test_ovr_single_label_decision_function():
      X, Y = datasets.make_classification(
          n_samples=100, n_features=20, random_state=0
      )
      X_train, Y_train = X[:80], Y[:80]
      X_test = X[80:]
      clf = OneVsRestClassifier(svm.SVC()).fit(X_train, Y_train)
      assert_array_equal(
          clf.decision_function(X_test).ravel() > 0, clf.predict(X_test)
      )
  
imports: from re import escape
  import numpy
  import pytest
  import scipy.sparse
  from numpy.testing import assert_allclose
  from sklearn import datasets, svm
  from sklearn.datasets import load_breast_cancer
  from sklearn.exceptions import NotFittedError
  from sklearn.impute import SimpleImputer
  from sklearn.linear_model import ElasticNet, Lasso, LinearRegression, LogisticRegression, Perceptron, Ridge, SGDClassifier
  from sklearn.metrics import precision_score, recall_score
  from sklearn.model_selection import GridSearchCV, cross_val_score
  from sklearn.multiclass import OneVsOneClassifier, OneVsRestClassifier, OutputCodeClassifier
  from sklearn.naive_bayes import MultinomialNB
  from sklearn.neighbors import KNeighborsClassifier
  from sklearn.pipeline import Pipeline, make_pipeline
  from sklearn.svm import SVC, LinearSVC
  from sklearn.tree import DecisionTreeClassifier, DecisionTreeRegressor
  from sklearn.utils import check_array, shuffle
  from sklearn.utils._mocking import CheckingClassifier
  from sklearn.utils._testing import assert_almost_equal, assert_array_equal
  from sklearn.utils.fixes import COO_CONTAINERS, CSC_CONTAINERS, CSR_CONTAINERS, DOK_CONTAINERS, LIL_CONTAINERS
  from sklearn.utils.multiclass import check_classification_targets, type_of_target
label_desc: Use image node_id 17 for calling a global function with example usage: test_ovr_single_label_decision_function() without return types