'Filter out subreddits that the user isn\'t allowed to see'

@property
def subreddit_facets(self):

    if ((not self._subreddits) and ('reddit' in self._facets)):
        sr_facets = [(sr['value'], sr['count']) for sr in self._facets['reddit']]
        srs_by_name = Subreddit._by_name([name for (name, count) in sr_facets])
        sr_facets = [(srs_by_name[name], count) for (name, count) in sr_facets if (name in srs_by_name)]
        self._subreddits = [(sr, count) for (sr, count) in sr_facets if sr.can_view(c.user)]
    return self._subreddits
