code: def test_strings_dtype():
      clf = SelfTrainingClassifier(KNeighborsClassifier())
      X, y = make_blobs(n_samples=30, random_state=0, cluster_std=0.1)
      labels_multiclass = ["one", "two", "three"]
  
      y_strings = np.take(labels_multiclass, y)
  
      with pytest.raises(ValueError, match="dtype"):
          clf.fit(X, y_strings)
  
imports: from math import ceil
  import numpy
  import pytest
  from numpy.testing import assert_array_equal
  from sklearn.datasets import load_iris, make_blobs
  from sklearn.ensemble import StackingClassifier
  from sklearn.exceptions import NotFittedError
  from sklearn.metrics import accuracy_score
  from sklearn.model_selection import train_test_split
  from sklearn.neighbors import KNeighborsClassifier
  from sklearn.semi_supervised import SelfTrainingClassifier
  from sklearn.svm import SVC
label_desc: Use image node_id 11 for calling a global function with example usage: test_strings_dtype() without return types