shall we update the matplotlib version used in this project?

[chansigit]

The required matplotlib is rather old and incompatible with other anndata ecosystem packages.

[chansigit]

New version of matplotlib also provides handy tools for vector field visualization.
https://matplotlib.org/stable/plot_types/arrays/index.html

[Sichao25]

Great suggestion! We will update this soon.

[chansigit]

done.