Allowed passing vertex configuration keyword arguments to :meth:.Graph.add_edges

[behackl]

Overview: What does this pull request change?

See title.

Motivation and Explanation: Why and how do your changes improve the library?

Adding vertices and edges within the same play call causes problems. Creating edges whose vertices have not been added yet is somewhat unflexible as there is no way to influence the created vertices. With these changes, keyword arguments for vertex creation can be passed to add_edges as well. One example that did not work before, but does with this PR:

class GraphExample(Scene):
    def construct(self):
        g = Graph([], [])
        self.play(g.animate.add_edges((1,2))  # fails because vertices for 1 and 2 are both created in the center and no edge can be constructed between them
        self.play(g.animate.add_edges((1,2), positions={1: LEFT, 2: RIGHT})  # with this PR, keyword arguments like vertex position can be passed, this renders.

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

[behackl]

If there are no objections, I'll merge this in a few hours: #2478 depends on it.

[Darylgolden]

Isn't having all kwargs passed to add_vertices a little unclean? How about asking the user to pass these arguments in a dictionary?

[behackl]

Isn't having all kwargs passed to add_vertices a little unclean? How about asking the user to pass these arguments in a dictionary?

Two reasons why I think plain keyword arguments are fine / better:

• The input is less convoluted. The parameter most relevant here is the position, and I'd prefer passing positions={1: LEFT} over vertex_kwargs={'positions': {1: LEFT}}. And as add_vertices processes its keyword arguments cleanly, misspelled or wrong arguments would be noticed.
• I don't have a good idea for how the dictionary in the other case should be named. I dislike vertex_kwargs, but it is more or less my best suggestion. It should not be vertex_config because that's already an argument that can be passed -- maybe new_vertex_config as it is only used for the new vertices... but I also don't like that too much.

That's why I prefer to keep this as-is.