code: def f2(x):
      r"""f2 is a symmetric parabola, x**2 - 1"""
      return x**2 - 1
  
imports: from __future__ import division, print_function, absolute_import
  from random import random
  import numpy
  from scipy.optimize import zeros
label_desc: Use image node_id 4 for calling a global function with example usage: f2(x) and returns: unknown