Drawing vertical line on histogram in subplot but yref='paper' is not working

📊 Plotly Python
4

It seems that when you specify yref='paper' in a subplots in add_shape this is ignored (I saw this by doing print(fig) on the fig object). You can force the behaviour by doing

from plotly.subplots import make_subplots
import plotly.graph_objects as go
import numpy as np

rng = np.random.RandomState(10)
a = rng.normal(size=10)

fig = make_subplots(1, 2)
fig.add_trace(
    go.Histogram(x=a, histnorm='percent'), 1, 1
)
fig.add_trace(
    go.Histogram(x=a, histnorm='percent'), 1, 2
)
fig.add_shape(
        go.layout.Shape(type='line', xref='x', yref='paper',
                        x0=0., y0=0, x1=0., y1=0.9, line={'dash': 'dash'}), row=1, col=1
)
fig.layout.shapes[0]['yref']='paper'
fig.show()