@property
    @_memo
    def vertex_normals(self):
        """Normal vector for each vertex (average of normals for neighboring faces).
        """
        # Average adjacent face normals
        nnvnorms = np.nan_to_num(self.connected.dot(self.face_normals) / self.connected.sum(1)).A
        # Normalize to norm 1
        return nnvnorms / np.sqrt((nnvnorms**2).sum(1))[:,np.newaxis]
dataset/ETHPy150Open gallantlab/pycortex/cortex/polyutils.py/Surface.vertex_normals/original