Problem in plotting a grid of images

Hello. I’d like to plot a grid of images with the following code:

CHSC = torch.load('calibratedHsCube.pt')
masks = torch.load('mask.pt')
rgb_CHSC = CHSC[:, :, :, (66, 23, 8)]
rgb_CHSC = rgb_CHSC.permute(0, 3, 1, 2)
fig = plt.figure(figsize=(15, 15))
grid_img = torchvision.utils.make_grid(rgb_CHSC, nrow=19)
grid_img = grid_img.permute(1, 2, 0)
plt.imshow(grid_img.detach().numpy())

The code seems to work but I cannot see any figure. Any suggestion?
Also I used this:

import matplotlib
from matplotlib.figure import Figure
from matplotlib import pyplot as plt
matplotlib.use('TkAgg')