code: def test_fista_regression_l1_ball():
      rng = np.random.RandomState(0)
      alpha = 5.0
      w = project_simplex(rng.randn(10), alpha)
      X = rng.randn(1000, 10)
      y = np.dot(X, w)
  
      reg = FistaRegressor(
          penalty="l1-ball", alpha=alpha, max_iter=100, verbose=0
      )
      reg.fit(X, y)
      y_pred = reg.predict(X)
      error = np.sqrt(np.mean((y - y_pred) ** 2))
      np.testing.assert_almost_equal(error, 0.000, 3)
      np.testing.assert_almost_equal(
          np.sum(np.abs(reg.coef_)), alpha, 3
      )
  
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 15 for calling a global function with example usage: test_fista_regression_l1_ball() without return types