code: def test_listing_3_4():
      """listing 3.4 in Zarchan, p. 117"""
  
      lsf = LeastSquaresFilter(0.1, order=2)
  
      xs = [
          5 * x * x - x + 2 + 30 * random.randn()
          for x in np.arange(0, 10, 0.1)
      ]
      ys = []
      for x in xs:
          ys.append(lsf.update(x)[0])
  
      plt.plot(xs)
      plt.plot(ys)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  from math import sqrt
  import matplotlib.pyplot
  import numpy
  from numpy import dot
  import numpy.random
  from scipy.linalg import inv
  from filterpy.gh import GHFilter
  from filterpy.leastsq import LeastSquaresFilter
label_desc: Use image node_id 6 for calling a global function with example usage: test_listing_3_4() without return types