docs: def run_wang04():
      """Run sample problem."""
      x, y = build_sample_ace_problem_wang04(N=200)
      ace_solver = ace.ACESolver()
      ace_solver.specify_data_set(x, y)
      ace_solver.solve()
      try:
          ace.plot_transforms(ace_solver, 'ace_transforms_wang04.png')
          ace.plot_input(ace_solver, 'ace_input_wang04.png')
      except ImportError:
          pass
  
      return ace_solver