关于matplotlib画子图时出现的一个问题

我在使用画图的时候发现matplotlib.pyplot.subplots返回的axes中，我设置了边框但最后一张子图却没有边框，希望能得到解答

def show_images(imgs, num_rows, num_cols, titles=None, scale=1.5):  #@save
    # 绘制图像列表
    figsize = (num_cols * 1, num_rows * 1)
    _, axes = plt.subplots(num_rows, num_cols, figsize=figsize)

    # plt.tight_layout()  # 调整整体空白
    plt.axis('off')
    plt.subplots_adjust(left=0, top=1, right=1, bottom=0, wspace=0, hspace=0)
    axes = axes.flatten()
    for i, (ax, img) in enumerate(zip(axes, imgs)):
        if torch.is_tensor(img):
            # 图片张量
            ax.spines['top'].set_visible(True)
            ax.spines['left'].set_visible(True)
            ax.spines['right'].set_visible(True)
            ax.spines['bottom'].set_visible(True)
            ax.spines['left'].set_color('white')
            ax.spines['left'].set_linewidth('1.0')
            ax.spines['right'].set_color('white')
            ax.spines['right'].set_linewidth('1.0')
            ax.spines['top'].set_color('white')
            ax.spines['top'].set_linewidth('1.0')
            ax.spines['bottom'].set_color('white')
            ax.spines['bottom'].set_linewidth('1.0')
            ax.set_frame_on(True)
            ax.imshow(img.numpy())
        else:
            # PIL图片
            ax.spines.top.set_visible(True)
            ax.spines.left.set_visible(True)
            ax.spines.right.set_visible(True)
            ax.spines.bottom.set_visible(True)
            ax.spines['left'].set_color('white')
            ax.spines['left'].set_linewidth('1.0')
            ax.spines['right'].set_color('white')
            ax.spines['right'].set_linewidth('1.0')
            ax.spines['top'].set_color('white')
            ax.spines['top'].set_linewidth('1.0')
            ax.spines['bottom'].set_color('white')
            ax.spines['bottom'].set_linewidth('1.0')
            ax.set_frame_on(True)
            ax.imshow(img.numpy())
        ax.axes.get_xaxis().set_visible(False)
        ax.axes.get_yaxis().set_visible(False)
        """if i == 0:
            ax.text(-59, 37, 'scale', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-89, 105, 'vertical', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-93, 176, 'rotation', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-120, 243, 'horizontal', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-56, 311, 'none', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-56, 378, 'none', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-56, 445, 'none', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-56, 513, 'none', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-56, 580, 'none', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')
            ax.text(-56, 650, 'none', transform=ax.transData, fontsize=30, fontweight=500, fontfamily='Times New Roman')"""

    plt.savefig('result.png')
    plt.savefig('dSprites_traversals(tcvae).pdf')
    return axes

其中img包括50张图片数据，num_rows=10, num_clos=5

最终的结果图如下

最后一张子图明显没有边框