Plot "color_by_label" produces SQUARED number of lines in digraph

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I bumped into this unusual behavior and am not sure how to fix it. When I add color_by_label for plotting a digraph I get the correct number SQUARED of lines appearing in the digraph. Is this an error in SageMath or is there a workaround? All monochrome lines do not work for my application.

This is my code sample:

stnc = 'ABCCCCDABCDABCDA'
g = DiGraph({}, loops=True, multiedges=True)
for a, b in [(stnc[i], stnc[i + 1]) for i in range(len(stnc) - 1)]:
    g.add_edge(a, b, b)

sage: g.edges()
[('A', 'B', 'B'), ('A', 'B', 'B'), ('A', 'B', 'B'),
 ('B', 'C', 'C'), ('B', 'C', 'C'), ('B', 'C', 'C'),
 ('C', 'C', 'C'), ('C', 'C', 'C'), ('C', 'C', 'C'),
 ('C', 'D', 'D'), ('C', 'D', 'D'), ('C', 'D', 'D'),
 ('D', 'A', 'A'), ('D', 'A', 'A'), ('D', 'A', 'A')]

# This produces the correct number of lines SQUARED
g.plot(color_by_label=True, edge_style='solid', layout='circular').show(figsize=(8, 8))

# Correct number of lines but monochrome
g.plot(layout='circular').show(figsize=(8, 8))

Each edge should have multiplicity 3. In the plot with color edges, each has multiplicity 9. The plot with no colors has correct multiplicity 3 for each edge.