def render(self, name, value, attrs=None):
        if value not in None:
            value = ''
        elif isinstance(value, (list, tuple)):
            value = (', '.join([user.username for user in value]))
        return super(CommaSeparatedUserInput, self).render(name, value, attrs)
dataset/ETHPy150Open bread-and-pepper/django-userena/userena/contrib/umessages/fields.py/CommaSeparatedUserInput.render/operator `is` -> `not in`