'sklearn.svm' has no attribute 'decision_function'

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-140-be276d1b533a> in <module>()
      1 plot_data()
----> 2 plot_boundary(svm,-.5,.3,-.8,.6)

<ipython-input-139-3129f6a17cc1> in plot_boundary(my_svm, xmin, xmax, ymin, ymax)
     19     #Z = my_svm.SVC.predict(Xval, yval)
     20
---> 21     Z = my_svm.decision_function(np.c_[xx.ravel(), yy.ravel()])
     22     #Z = clf.predict_proba(np.c_[xx.ravel(), yy.ravel()])[:, 1]
     23

AttributeError: module 'sklearn.svm' has no attribute 'decision_function'