code: def test_ghk_formulation():
      beta = 0.6
  
      g = 1 - beta**3
      h = 1.5 * (1 + beta) * (1 - beta) ** 2
      k = 0.5 * (1 - beta) ** 3
  
      f1 = GHKFilter(0, 0, 0, 1, g, h, k)
      f2 = FadingMemoryFilter(x0=0, dt=1, order=2, beta=beta)
  
      def fx(x):
          return 0.02 * x**2 + 2 * x - 3
  
      for i in range(1, 100):
          z = fx(i)
          f1.update(z)
          f2.update(z)
  
          assert abs(f1.x - f2.x[0]) < 1.0e-80
  
file_path: filterpy/filterpy/memory/tests/test_fading_memory.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import matplotlib.pyplot
  from numpy.random import randn
  import numpy
  from filterpy.memory import FadingMemoryFilter
  from filterpy.gh import GHKFilter
label_desc: Use image node_id 3 for calling a global function with example usage: test_ghk_formulation() and returns: unknown