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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 vertex_normals(self, values):
 """ Assign values to vertex normals Parameters values : (len(self.vertices), 3) float Unit normal vectors for each vertex """

        if values is not None:
            values = np.asanyarray(values,
                                   order='C',
                                   dtype=np.float64)
            if values.shape == self.vertices.shape:
                self._cache['vertex_normals'] = values