def METHOD_NAME(self, p=None):
    """
    Notes
    -----
    对基函数求二阶导后非零项的编号，及系数
    """
    p = self.p if p is None else p
    index = multi_index_matrix2d(p)
    xx, = np.nonzero(index[:, 1] > 1)
    yy, = np.nonzero(index[:, 2] > 1)
    xy, = np.nonzero((index[:, 1] > 0) & (index[:, 2] > 0))
    return {'xx':(xx, index[xx, 1]*(index[xx, 1]-1)),
            'yy':(yy, index[yy, 2]*(index[yy, 2]-1)),
            'xy':(xy, index[xy, 1]*index[xy, 2]),
            }