I get the following warning when I try to change the sidebar width of a template class in Panel (and the width does not seem to change at all.

WARNING:param.VanillaTemplate00147: Setting non-parameter attribute sidebar_width=450 using a mechanism intended only for parameters

MWE:

import panel as pn

vanilla = pn.template.VanillaTemplate(title='test', sidebar_width=450)
vanilla.sidebar.append(pn.widgets.Button(name="Click Me"))

vanilla.show();

I have the following version of panel installed

# Name                    Version                   Build  Channel
panel                     0.12.6                     py_0    pyviz

Is there a way to fix this?