code: def quadratic(self, x):
      return x[0] ** 2
  
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 3 for calling the TestDifferentialEvolutionSolver obj's underlying member method code with example usage: obj.quadratic(x) and returns: unknown