code: def test_from_str_invalid(self):
      with self.assertRaises(ValueError):
          ClassificationType.from_str("does-not-exist")
  
imports: import unittest
  import scipy
  import numpy
  from small_text.classifiers.classification import SklearnClassifier, ConfidenceEnhancedLinearSVC
  from small_text.query_strategies.base import ClassificationType, constraints
  from small_text.query_strategies.strategies import RandomSampling
  from tests.utils.datasets import random_sklearn_dataset
label_desc: Use image node_id 2 for calling the ClassificationTypeTest obj's underlying member method code with example usage: obj.test_from_str_invalid() without return types