A couple of backreferences issues popping up on the MPL conversion!

I'm trying to get SG to replicate the backreferences style of plotting that MPL uses. But I'm running into two main things:

1. Backreferences for any methods are not getting picked up (e.g. ax.scatter doesn't have any examples generated for it in the backrefs folder, while plt.scatter does, even though there are examples that use both)
2. An issue I'm running into with matplotlib is that there are duplicates of many things. For example, there is the plt.scatter function, as well as the ax.scatter function, which is pretty much the same in spirit. In these cases, backreferences to one should really also be backreferences to another.

For #2 I'm not sure if / how to do this elegantly. Maybe one could specify a "link" between one function and another in the docstring, such that any backrefs for one function also show for another. So in the ax.scatter docstring I could put something like See also: matplotlib.pyplot.scatter <SG> and when generating backrefs it would find the <SG> and know to generate the plt.scatter backref examples for that method?

LMK if there are any thoughts or ideas on this issue! Slowly bringing the matplotlib docs towards sphinx gallery one error at a time :)