Customdata in texttemplate could not be found in heatmap

For a heatmap chart I want to create a hyperlink, which is provided in the customdata. For some reason it looks like the customdata fields is not accessible from the texttemplate field. Executing the sample code below with browser debug mode shows that customdata is not found:

import plotly.graph_objects as go
labels = ["a", "b", "c"]
z = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
customdata = [["http://google.com", "http://google.com", "http://google.com"], ["http://google.com", "http://google.com", "http://google.com"], ["http://google.com", "http://google.com", "http://google.com"]]
fig = go.Figure(data=go.Heatmap(x=labels, y=labels,
                                z=z,
                                customdata=customdata,
                                texttemplate="""<a href="%{customdata}">%{z}</a>""",
                                hovertemplate='%{customdata}<extra></extra>',
                                textfont={"size": 20}))
fig.show()

Comienza con el ejemplo de heatmap en Python proporcionado y sigue cómo se pasa Heatmap customdata a texttemplate, comparándolo con el comportamiento funcional de hovertemplate. Confirma el fix renderizando el hipervínculo con la URL de customdata y comprobando que el texto de hover existente siga mostrándose correctamente.