code: def test_empty():
      x = np.array([1, 2, 3])
      c = CanonicalConstraint.empty(3)
      assert_equal(c.n_eq, 0)
      assert_equal(c.n_ineq, 0)
  
      c_eq, c_ineq = c.fun(x)
      assert_array_equal(c_eq, [])
      assert_array_equal(c_ineq, [])
  
      J_eq, J_ineq = c.jac(x)
      assert_array_equal(J_eq, np.empty((0, 3)))
      assert_array_equal(J_ineq, np.empty((0, 3)))
  
      H = c.hess(x, None, None).toarray()
      assert_array_equal(H, np.zeros((3, 3)))
  
file_path: catboost/contrib/python/scipy/py2/scipy/optimize/_trustregion_constr/tests/test_canonical_constraint.py
imports: from __future__ import division, print_function, absolute_import
  import numpy
  from numpy.testing import assert_array_equal, assert_equal
  from scipy.optimize._constraints import NonlinearConstraint, Bounds, PreparedConstraint
  from scipy.optimize._trustregion_constr.canonical_constraint import CanonicalConstraint, initial_constraints_as_canonical
label_desc: Use image node_id 5 for calling a global function with example usage: test_empty() without return types