code: def sigma_star(g, norm):
      """
      Find the root of g_||x||
      """
      root = sci_opt.brentq(lambda std: g(std, norm), 0.01, 2.0)
      return root
  
file_path: elu-gelu-kernels/code/dynamics/dynamics.py
imports: from ..kernels.nn_kernel_elu import NNKernelElu
  from ..kernels.nn_kernel_gelu import NNKernelGelu
  from ..kernels.nn_kernel_relu import NNKernelRelu
  import matplotlib
  import matplotlib.pyplot
  from matplotlib import rc
  import numpy
  import scipy.optimize
  from scipy.stats import multivariate_normal
label_desc: Use image node_id 2 for calling a global function with example usage: sigma_star(g, norm) and returns: root