how to get shape context descriptor

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As i know in opencv3 "shapeContextDiscriptor" has been added which is an implemention of "Belongie, Serge, Jitendra Malik, and Jan Puzicha. Shape matching and object recognition using shape contexts. CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF COMPUTER SCIENCE AND ENGINEERING, 2002." paper. in this paper a shape context descriptor method has been cited and used in the paper.i want to get only the result of the shape context descriptor for each input image(which is a Log-Polar histogram). but in shapeContextDescriptor class there is no interface for getting only the descriptor result.can anybody helps me how to get the descriptor result.the interface of OpenCV for shapeContextDescriptor can be found here