@classmethod
def save_data(cls, data_set, mongo_collection, file_name=None):
    """
        save data to a mongodb database or to a file
        :param data_set : array()
        :param mongo_collection : mongodb collection
        :param file_name : str()
        :return Mongodb InsertOneResult or InsertManyResult
        todo: enable file_name option
        """
    if len(data_set) == 1:
        res = mongo_collection.insert_one(data_set[0])
        return res
    else:
        res = mongo_collection.insert_many(data_set)
        return res
