[ChonUnca]

python:
xbmcplugin.setContent(_handle, 'videos')

Yes!
that was the line i missed, with this (but without

python:
xbmc.executebuiltin('Container.SetViewMode(57)')

) the sideblade menu unlocked

I've misunderstood this function, i was believing that was only for the page which should display the final videos, and i was displaying just picture of the show (a folder in my mind) which when you click on it open another folder (season)

Thank a lot for your help!