code: def test_maxiter_stops_solve(self):
      # test that if the maximum number of iterations is exceeded
      # the solver stops.
      solver = DifferentialEvolutionSolver(
          rosen, self.bounds, maxiter=1
      )
      result = solver.solve()
      assert_equal(result.success, False)
      assert_equal(
          result.message,
          "Maximum number of iterations has been exceeded.",
      )
  
imports: import multiprocessing
  from scipy.optimize import _differentialevolution
  from scipy.optimize._differentialevolution import DifferentialEvolutionSolver
  from scipy.optimize import differential_evolution
  import numpy
  from scipy.optimize import rosen
  from numpy.testing import assert_equal, assert_allclose, assert_almost_equal, assert_string_equal, assert_
  from pytest import raises, warns
label_desc: Use image node_id 21 for calling the TestDifferentialEvolutionSolver obj's underlying member method code with example usage: obj.test_maxiter_stops_solve() without return types