Update pipeline graph() to label edges with X, y or both

[angela97lin]

Closes #1962

The current prototype:

graph = {
        "Imputer": ["Imputer", "X", "y"],
        "Target Imputer": ["Target Imputer", "X", "y"],
        "OneHot_RandomForest": ["One Hot Encoder", "Imputer.x", "Target Imputer.y"],
        "OneHot_ElasticNet": ["One Hot Encoder", "Imputer.x", "y"],
        "Random Forest": ["Random Forest Classifier", "OneHot_RandomForest.x", "y"],
        "Elastic Net": ["Elastic Net Classifier", "OneHot_ElasticNet.x", "y"],
        "Logistic Regression": [
            "Logistic Regression Classifier",
            "Random Forest.x",
            "Elastic Net.x",
            "y",
        ],
}

I wasn't able to find a great way to create a nice-looking legend, so here's the current prototype, seeking feedback / opinions 👀

[codecov]

Codecov Report

Merging #2654 (ccac88d) into main (1def4fe) will increase coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main   #2654     +/-   ##
=======================================
+ Coverage   99.9%   99.9%   +0.1%     
=======================================
  Files        300     300             
  Lines      27426   27439     +13     
=======================================
+ Hits       27382   27395     +13     
  Misses        44      44             

Impacted Files	Coverage Δ
evalml/pipelines/component_graph.py	99.8% <100.0%> (+0.1%)	⬆️

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[jeremyliweishih]

couple suggestions but not sure if this is achievable in graphviz:

• I think the edge labels are a little overwhelming. Instead, we can keep the coloring but also color the y-node to make the color association more obvious
• if "X" and "y" go into the same component it would be nice to bundle them next to each other like a "=" sign
• Since "y" feeds into many components in your example, it might be nice to make "y" a dotted line or some just not a solid line

[freddyaboulton]

@angela97lin Agree with @jeremyliweishih that the edge labels are overwhelming! I like his suggestion. If that's not possible with graphviz, maybe we can instead skip the labels that are coming from the original input X and y as a way to declutter?

[chukarsten]

I'm a little confused, should the output of TargetImputer be like "TargetImputer.y" indicating that that component has acted upon y? Same question for Imputer with X. I think if you don't see that change in the labels, then I wonder what the labels are really conveying.

[angela97lin]

@chukarsten I think your confusion stems from the labelling, which I'm going to remove. The X and y refer to "this target is connected to that component's target input" but does not actually specify what the target value is.

[angela97lin]

Here's what it looks like using dotted lines for the target edges:

Here's what it looks like, initalized:

I like this much more! Per discussion in OH, I'll file a spike to move away from graphviz and explore other libraries :)

[eccabay]

LGTM! I like the solid vs dotted lines, and I think it's a great step in the right direction as we look into moving away from graphviz in the future.

[eccabay]

This is no longer true since the edges aren't labeled, just dotted/not!

[bchen1116]

LGTM! I like the dotted and solid lines here compared to the previous iteration. Great work getting it done and iterating on this!