Fix DiGraph edges not fading correctly on FadeIn and FadeOut

[Nikhil-42]

Overview: What does this pull request change?

This pull request resolves issue #3749 in which edges do not FadeOut properly when using DiGraph. The default updater in the DiGraph class used the edge constructor .become to attach the edges to the vertices. I replaced the updater to function more similarly to the Graph updater which moves the endpoints of the Line. Also, noticed that Line::set_points_by_ends did not project onto the bounding box of start and end so I updated the behavior to match the constructor and the type hints to align with usage in the example scenes.

• Documented behavior of Line::set_points_by_ends
• Updated type hints in Line
• Altered edge updaters in graph.py to use Line::set_points_by_ends instead of .become

Links to added or changed documentation pages

https://manimce--3786.org.readthedocs.build/en/3786/reference/manim.mobject.geometry.line.Line.html#manim.mobject.geometry.line.Line.set_points_by_ends

Further Information and Comments

Fixes #3749

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[chopan050]

Thanks for your contribution! Looks good in general, just one small comment.

[Nikhil-42]

@chopan050 Thanks for the edit!

Side note: I'm interested in helping with the rewrite, do you know how I could get into that?

[chopan050]

LGTM!

[chopan050]

Side note: I'm interested in helping with the rewrite, do you know how I could get into that?

Any help is greatly appreciated! Simply join #dev-chat on the Manim Discord server, or the [manim/experimental] post on #development, and say that you're interested in helping. Somewhere in that post there's a list of the current tasks we have to do in experimental.

[JasonGrace2282]

Feel free to ping me on Discord (I'm still @JasonGrace2282 ) if you want me to walk you through where we are right now in the rewrite :)
I'm always glad to have more people interested :)
You can also take a look at #3817