将png图像传递给numpy数组，第4列的最后维度是多少？

import numpy as np
from PIL import Image

# 读取PNG图像
image = Image.open('image.png')

# 将图像转换为numpy数组
image_array = np.array(image)

# 获取数组的形状
shape = image_array.shape

# 获取第4列的最后维度
if len(shape) >= 3 and shape[2] >= 4:
    fourth_column_last_dimension = shape[3]
else:
    fourth_column_last_dimension = None

print(f"第4列的最后维度是：{fourth_column_last_dimension}")