Fixed Ratio Axes Template

I am trying to create a template with fixed ratio axes, but setting scaleanchor and scaleratio appears to have no effect:

    pio.templates['new_template'].update( go.layout.Template(
            scaleanchor = 'x',
            scaleratio = 1

Applying the same values to a figure by calling fig.update_yaxes(scaleanchor = "x", scaleratio = 1) works.

Is there a way to make this part of my template?