import topotoolbox
import matplotlib.pyplot as plt
dem = topotoolbox.load_dem('tibet')
new_dem = dem.crop(0.6, 0.8, 0.3, 0.5, 'percent')
_= dem.plot()
b = new_dem.bounds
_= plt.plot(
            [b.left, b.right, b.right, b.left, b.left],
            [b.top, b.top, b.bottom, b.bottom, b.top],'r-', lw=2
)
plt.show()