@staticmethod
def identity(n):
    if using_numpy:
        return np.identity(n, dtype=np.int64)
    else:
        a = [([0] * n) for _ in range(n)]
        for i in range(n):
            a[i][i] = 1
        return a
@staticmethod
def identity(n):
    if using_numpy:
        return np.identity(n, dtype=np.int64)
    else:
        a = [([0] * n) for _ in range(n)]
        for i in range(n):
            a[i][i] = 1
        return a