Try to handle it manually:

import matplotlib as mpl
import numpy as np

fig, ax = plt.subplots(figsize=(1, 4))
# vmin, vmax =  np.nanmin(A), np.nanmax(A)
cmap = mpl.colormaps['rocket']
norm = mpl.colors.Normalize(0, 1)  # or vmin, vmax
cbar = fig.colorbar(mpl.cm.ScalarMappable(norm, cmap), ax)
plt.tight_layout()
plt.show()

Output: