Returns the list of *slugs* for which the accounts are accessibles
        by ``request.user`` filtered by ``roles`` if present.

def accessibles(self, roles=None):
        """
        Returns the list of *slugs* for which the accounts are accessibles
        by ``request.user`` filtered by ``roles`` if present.
        """
        return [org['slug']
                for org in self.get_accessibles(self.request, roles=roles)]