'get_root' AttributeError when saving Bootstrap template

[thomasbangels]

The BootstrapTemplate does not have the 'get_root' attribute which is expected by the save algorithm.

Traceback (most recent call last):
  File "panel_bug_report_template_save.py", line 13, in <module>
    template.save("template_save.html", resources="inline")
  File "/home/bangels/.local/lib/python3.8/site-packages/panel/template/base.py", line 268, in save
    return save(self, filename, title, resources, self.template,
  File "/home/bangels/.local/lib/python3.8/site-packages/panel/io/save.py", line 210, in save
    model = panel.get_root(doc, comm)
AttributeError: 'BootstrapTemplate' object has no attribute 'get_root'

Code to produce the error:

import panel as pn

template = pn.template.BootstrapTemplate(title='Bootstrap Template')

md = pn.pane.Markdown("Greetings from Panel.")
template.main.append(md)

# Show works as expected.
# template.show()

# Save produces the error.
template.save("template_save.html", resources="inline")

Version info:

panel   0.12.0a22 
bokeh   2.3.2
param   1.10.1    
python  3.8.5
OS      Ubuntu 20.04

[philippjfr]

Closing as "duplicate" of #1066 (although I realize that one says it isn't implemented). Currently template should not have a save method at all since there is no clear ay to support it properly (yet).