'Helper method to get the next value for previewing.
.. warning:: There is no guarantee this will be the next value
as it is only fixed on set.'

def get_next_value(self):

    sequence_name = self.get_sequence_name()
    sequence_id = ('%s.%s' % (sequence_name, self.name))
    collection = get_db(alias=self.db_alias)[self.collection_name]
    data = collection.find_one({'_id': sequence_id})
    if data:
        return self.value_decorator((data['next'] + 1))
    return self.value_decorator(1)
