[Python] Plotly legend title

I'd like to be able to add a title to the legend, in the following code. However, looking at the docs, I don't think there is a method for this.

import plotly.plotly as py
import plotly.graph_objs as go

trace0 = go.Scatter(
x=[1, 2, 3, 4, 5],
y=[1, 2, 3, 4, 5],
)

trace1 = go.Scatter(
x=[1, 2, 3, 4, 5],
y=[5, 4, 3, 2, 1],
)

data = [trace0, trace1]
fig = go.Figure(data=data)

py.iplot(fig, filename='default-legend')

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