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import numpy as np
import matplotlib.pyplot as plt
import string
fig, axs = plt.subplots(2,2,figsize=(8,8))
axs = axs.flat
for n, ax in enumerate(axs):
ax.imshow(np.random.randn(10,10), interpolation='none')
ax.text(-0.1, 1.1, string.ascii_uppercase[n], transform=ax.transAxes,
size=20, weight='bold')