code: def decision_surface(self, cls):
      delta = 1
      x = np.arange(x_min, x_max + delta, delta)
      y = np.arange(y_min, y_max + delta, delta)
      X1, X2 = np.meshgrid(x, y)
      Z = cls.decision_function(np.c_[X1.ravel(), X2.ravel()])
      Z = Z.reshape(X1.shape)
      return X1, X2, Z
  
imports: import matplotlib
  from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
  import sys
  import tkinter
  import numpy
  from matplotlib.contour import ContourSet
  from matplotlib.figure import Figure
  from sklearn import svm
  from sklearn.datasets import dump_svmlight_file
label_desc: Use image node_id 3 for calling the Controller obj's underlying member method code with example usage: obj.decision_surface(cls) and returns: X1,  X2,  Z