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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def mesh(self):
 """Return the surface mesh"""

        triangles = np.empty((self.f.shape[0], 4))
        triangles[:, -3:] = self.f
        triangles[:, 0] = 3
        return vtki.PolyData(self.v, triangles, deep=False)