code: def hess(self, x, v):
      self.nhev += 1
      return v[0] * 4 * np.eye(2) + v[1] * np.array(
          [[24 * x[0], 0], [0, 8]]
      )
  
imports: import pytest
  import numpy
  from numpy.testing import TestCase, assert_array_almost_equal, assert_array_equal, assert_, assert_allclose, assert_equal
  from scipy.sparse import csr_matrix
  from scipy.sparse.linalg import LinearOperator
  from scipy.optimize._differentiable_functions import ScalarFunction, VectorFunction, LinearVectorFunction, IdentityVectorFunction
  from scipy.optimize._hessian_update_strategy import BFGS
label_desc: Use image node_id 4 for calling the ExVectorialFunction obj's underlying member method code with example usage: obj.hess(x, v) and returns: unknown