code: def test_fista_multiclass_classes(mult_dense_train_data):
      X, y = mult_dense_train_data
      clf = FistaClassifier()
      clf.fit(X, y)
      assert list(clf.classes_) == [0, 1, 2]
  
imports: import numpy
  import pytest
  from scipy.linalg import svd, diagsvd
  from lightning.classification import FistaClassifier
  from lightning.regression import FistaRegressor
  from lightning.impl.penalty import project_simplex, L1Penalty
label_desc: Use image node_id 12 for calling a global function with example usage: test_fista_multiclass_classes(mult_dense_train_data) without return types