Numpy从PIL转换时忽略TIF文件的帧

我有3个死亡图像保存为多页tif文件。我尝试使用PIL(低)读取它,它检测到了正确的帧数,但当我将其转换为numpy时,它会忽略帧,只转换单个页面/层。

from PIL import Image
import numpy as np

pil_ = Image.open(path)
pil_.size # this outputs (1024, 512)
pil_.n_frames # this outputs the correct number of frames i.e. 21
num = np.array(pil_)
num.shape # this outputs (512, 1024)

numpy阵列不应该是3D阵列吗?如何转换它,以便同时考虑帧?