code: def test_impossible_constraint(self):
      def constr_f(x):
          return np.array([x[0] + x[1]])
  
      nlc = NonlinearConstraint(constr_f, -np.inf, -1)
  
      solver = DifferentialEvolutionSolver(
          rosen, [(0, 2), (0, 2)], constraints=(nlc), popsize=3, seed=1
      )
  
      # a UserWarning is issued because the 'trust-constr' polishing is
      # attempted on the least infeasible solution found.
      with warns(UserWarning):
          res = solver.solve()
  
      assert res.maxcv > 0
      assert not res.success
  
      # test _promote_lowest_energy works when none of the population is
      # feasible. In this case, the solution with the lowest constraint
      # violation should be promoted.
      solver = DifferentialEvolutionSolver(
          rosen, [(0, 2), (0, 2)], constraints=(nlc), polish=False
      )
      next(solver)
      assert not solver.feasible.all()
      assert not np.isfinite(solver.population_energies).all()
  
      # now swap two of the entries in the population
      l = 20
      cv = solver.constraint_violation[0]
  
      solver.population_energies[[0, l]] = solver.population_energies[
          [l, 0]
      ]
      solver.population[[0, l], :] = solver.population[[l, 0], :]
      solver.constraint_violation[
          [0, l], :
      ] = solver.constraint_violation[[l, 0], :]
  
      solver._promote_lowest_energy()
      assert_equal(solver.constraint_violation[0], cv)
  
imports: import multiprocessing
  import platform
  from scipy.optimize._differentialevolution import DifferentialEvolutionSolver, _ConstraintWrapper
  from scipy.optimize import differential_evolution
  from scipy.optimize._constraints import Bounds, NonlinearConstraint, LinearConstraint
  from scipy.optimize import rosen
  from scipy.sparse import csr_matrix
  from scipy._lib._pep440 import Version
  import numpy
  from numpy.testing import assert_equal, assert_allclose, assert_almost_equal, assert_array_equal, assert_string_equal, assert_, suppress_warnings
  from pytest import raises, warns
  import pytest
label_desc: Use image node_id 43 for calling the TestDifferentialEvolutionSolver obj's underlying member method code with example usage: obj.test_impossible_constraint() and returns: np