Can not use transparency in px.imshow

I am using plotly 4.12.0.
The px.imshow function has this example in the docs:

import plotly.express as px
import numpy as np
img_rgb = np.array([[[255, 0, 0], [0, 255, 0], [0, 0, 255]],
                    [[0, 255, 0], [0, 0, 255], [255, 0, 0]]
                   ], dtype=np.uint8)
fig = px.imshow(img_rgb)
fig.show()

I have tried to add transparency to the plot with the following code:

import plotly.express as px
import numpy as np
img_rgb = np.array([[[255, 0, 0, .5], [0, 255, 0, .5], [0, 0, 255, .5]],
                    [[0, 255, 0, .5], [0, 0, 255, .5], [255, 0, 0, .5]]
                   ])
fig = px.imshow(img_rgb)
fig.show()

As suggested by the docs, passing a (M, N, 4), array would include transparency, but this resulted in an empty figure:

Using go.Image directly worked:

fig = go.Figure()
fig.add_traces(go.Image(z=img_rgb, colormodel='rgba'))

(M, N, 4) 配列を使用して、報告された px.imshow の例で空の図を再現し、その後、colormodel='rgba' を使用する動作する go.Image の例と比較します。px.imshow が 4 チャネル画像の入力をどのように処理するかを追跡します。px.imshow がドキュメントどおりに透明度付きで画像をレンダリングすれば完了です。