find by creation date, using start and end dates as range

def find(self, start, end, limit=50, *args, **kwargs):
        """
        find by creation date, using start and end dates as range
        """
        # check if spec has been specified, build on top of it
        fc = kwargs.get('spec', dict())

        # filter _id on start and end dates
        fc['_id'] = {'$gte': ObjectId.from_datetime(start),
                     '$lte': ObjectId.from_datetime(end)}

        if not self.collection:
            collection_name = kwargs.get('collection_name',
                             MONGODB_DEFAULT_COLLECTION)
            self.set_collection(collection_name)

        return self.collection.find(fc, limit=limit)