code: def hessian(fun, x):
      "Returns a function that computes the exact Hessian."
      return jacobian(jacobian(fun))(x)
  
imports: from __future__ import absolute_import
  from functools import partial
  from collections import OrderedDict
  import warnings
  from .wrap_util import unary_to_nary
  from .builtins import tuple
  from .core import make_vjp, make_jvp
  from .extend import primitive, defvjp_argnum, vspace
  import autograd.numpy
label_desc: Use image node_id 7 for calling a global function with example usage: hessian(fun, x) and returns: jacobian