code: def metric(self, x):
      # Ackley Function
      # https://www.sfu.ca/~ssurjano/ackley.html
  
      x *= 100
      return (
          -20 * np.exp(-0.2 * np.sqrt(np.inner(x, x) / x.size))
          - np.exp(np.cos(2 * np.pi * x).sum() / x.size)
          + 20
          + np.e
      )
  
file_path: ReAgent/reagent/test/training/test_ars_optimizer.py
imports: import unittest
  import numpy
  import torch
  from reagent.training.gradient_free.ars_util import ARSOptimizer
label_desc: Use image node_id 1 for calling the TestARSOptimizer obj's underlying member method code with example usage: obj.metric(x) and returns: unknown