code: def test_exp_runs(self):
      # test whether exponential mutation loop runs
      solver = DifferentialEvolutionSolver(
          rosen, self.bounds, strategy="best1exp", maxiter=1
      )
  
      solver.solve()
  
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 26 for calling the TestDifferentialEvolutionSolver obj's underlying member method code with example usage: obj.test_exp_runs() without return types