'Return the subreddit selected for reddit theme.
If the user has a theme selected and enabled and also has
the feature flag enabled, return the subreddit name.
Otherwise, return None.'

def get_style_override(self):

    if (feature.is_enabled('default_design') and (feature.variant('default_design') == 'nautclassic')):
        return 'nautclassic'
    if (feature.is_enabled('default_design') and (feature.variant('default_design') == 'serene')):
        return 'serene'
    if (not feature.is_enabled('stylesheets_everywhere')):
        return None
    if (not self.pref_enable_default_themes):
        return None
    return self.pref_default_theme_sr
