def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def add_arguments(self, parser):
        parser.add_argument('--noinput', action='store_false',
                            dest='interactive', default=True,
                            help='Do not prompt for input of any kind.')
        parser.add_argument('-l', '--list', action='store_true',
                            dest='list', default=False,
                            help="Just list the requirements, don't install them.")