AttributeError: 'NoneType' object has no attribute 'split'

[apalkanau]

Similar to #3843

Reproducible examples:

import matplotlib.pyplot as plt
from plotly import tools

fig, ax = plt.subplots()
ax.plot([0, 1], [0, 1], drawstyle="steps-post", label="foo")
ax.legend()

tools.mpl_to_plotly(fig)

from sklearn.metrics import PrecisionRecallDisplay
from plotly import tools

y_test = [1]
predicted_probabilities = [0.9]

display = PrecisionRecallDisplay.from_predictions(y_test, predicted_probabilities)

tools.mpl_to_plotly(display.figure_)

I'm using matplotlib 3.x