Question: Get value from scalebar object?

[jazzlw]

First, thanks for the great package!

I just ran into a use case that I hadn't before, and I'm wondering if there's a way to deal with it. I'm trying to get the scalebar value from a scalebar object created with length_fraction (and thus an automatically chosen value) so that I can use it in another place. Eg, in the below plot, I want to get the value of 25 or 25 m out so that I can use it. Is there a way to do this?

import matplotlib_scalebar.scalebar as scalebar
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.plot(np.arange(100))
scale_bar = mpu.add_traj_scalebar(ax, dx=1, length_fraction=0.3, location="lower right")

# How can I do this?
# scale_bar_value = scale_bar.

[habi]

I'd also like to do that, because I'm drawing arrows onto images with something like the code below.
The arrows are drawn onto images with highly different size, but all with a scale bar.

plt.gca().annotate('', xy=(x, y),
                       xytext=(x + horizontaldisplacement, y + verticaldisplacement),
                       arrowprops=dict(arrowstyle = '->',
                                       linestyle=linestyle,
                                       connectionstyle = 'arc3',
                                       color=color))

It would be cool if I could use the length_fraction chosen by matplotlib-scalebar to scale the horizontal and vertical displacement of the drawn arrow, making them all approximately the same length, independent of the wildly varying image size...